regulator: dt-bindings: mt6357: Drop fixed compatible requirement

Some of the regulators on the MT6357 PMIC currently reference the
fixed-regulator dt-binding, which enforces the presence of a
regulator-fixed compatible. However since all regulators on the MT6357
PMIC are handled by a single mt6357-regulator driver, probed through
MFD, the compatibles don't serve any purpose. In fact they cause
failures in the DT kselftest since they aren't probed by the fixed
regulator driver as would be expected. Furthermore this is the only
dt-binding in this family like this: mt6359-regulator and
mt6358-regulator don't require those compatibles.

Commit d77e89b7b03f ("arm64: dts: mediatek: mt6357: Drop regulator-fixed
compatibles") removed the compatibles from Devicetree, but missed
updating the binding, which still requires them, introducing dt-binding
errors. Remove the compatible requirement by referencing the plain
regulator dt-binding instead to fix the dt-binding errors.

Fixes: d77e89b7b03f ("arm64: dts: mediatek: mt6357: Drop regulator-fixed compatibles")
Signed-off-by: Nícolas F. R. A. Prado <[e-mail]>
Link: https://patch.msgid.link/20250514-mt635[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

Documentation/devicetree/bindings/regulator/mediatek,mt6357-regulator.yaml

···
 
   "^ldo-v(camio18|aud28|aux18|io18|io28|rf12|rf18|cn18|cn28|fe28)$":
     type: object
-    $ref: fixed-regulator.yaml#
+    $ref: regulator.yaml#
     unevaluatedProperties: false
     description:
       Properties for single fixed LDO regulator.
···
           regulator-enable-ramp-delay = <220>;
         };
         mt6357_vfe28_reg: ldo-vfe28 {
-          compatible = "regulator-fixed";
           regulator-name = "vfe28";
           regulator-min-microvolt = <2800000>;
           regulator-max-microvolt = <2800000>;
···
           regulator-enable-ramp-delay = <110>;
         };
         mt6357_vrf18_reg: ldo-vrf18 {
-          compatible = "regulator-fixed";
           regulator-name = "vrf18";
           regulator-min-microvolt = <1800000>;
           regulator-max-microvolt = <1800000>;
           regulator-enable-ramp-delay = <110>;
         };
         mt6357_vrf12_reg: ldo-vrf12 {
-          compatible = "regulator-fixed";
           regulator-name = "vrf12";
           regulator-min-microvolt = <1200000>;
           regulator-max-microvolt = <1200000>;
···
           regulator-enable-ramp-delay = <264>;
         };
         mt6357_vcn28_reg: ldo-vcn28 {
-          compatible = "regulator-fixed";
           regulator-name = "vcn28";
           regulator-min-microvolt = <2800000>;
           regulator-max-microvolt = <2800000>;
           regulator-enable-ramp-delay = <264>;
         };
         mt6357_vcn18_reg: ldo-vcn18 {
-          compatible = "regulator-fixed";
           regulator-name = "vcn18";
           regulator-min-microvolt = <1800000>;
           regulator-max-microvolt = <1800000>;
···
           regulator-enable-ramp-delay = <264>;
         };
         mt6357_vcamio_reg: ldo-vcamio18 {
-          compatible = "regulator-fixed";
           regulator-name = "vcamio";
           regulator-min-microvolt = <1800000>;
           regulator-max-microvolt = <1800000>;
···
           regulator-always-on;
         };
         mt6357_vaux18_reg: ldo-vaux18 {
-          compatible = "regulator-fixed";
           regulator-name = "vaux18";
           regulator-min-microvolt = <1800000>;
           regulator-max-microvolt = <1800000>;
           regulator-enable-ramp-delay = <264>;
         };
         mt6357_vaud28_reg: ldo-vaud28 {
-          compatible = "regulator-fixed";
           regulator-name = "vaud28";
           regulator-min-microvolt = <2800000>;
           regulator-max-microvolt = <2800000>;
           regulator-enable-ramp-delay = <264>;
         };
         mt6357_vio28_reg: ldo-vio28 {
-          compatible = "regulator-fixed";
           regulator-name = "vio28";
           regulator-min-microvolt = <2800000>;
           regulator-max-microvolt = <2800000>;
           regulator-enable-ramp-delay = <264>;
         };
         mt6357_vio18_reg: ldo-vio18 {
-          compatible = "regulator-fixed";
           regulator-name = "vio18";
           regulator-min-microvolt = <1800000>;
           regulator-max-microvolt = <1800000>;