dt-bindings: simplefb: Support regulator supply properties

The physical display tied to the framebuffer may have regulators
providing power to it, such as power for LCDs or interface conversion
chips.

The number of regulators in use may vary, but the regulator supply
binding can not be a list. Instead just support any named regulator
supply properties under the device node. These should be properly
named to match the device schematics / design. The driver should
take care to go through them all.

Signed-off-by: Chen-Yu Tsai <[e-mail]>
Reviewed-by: Hans de Goede <[e-mail]>
Acked-by: Mark Brown <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Signed-off-by: Tomi Valkeinen <[e-mail]>

Documentation/devicetree/bindings/display/simple-framebuffer.txt

···
   - a8b8g8r8 (32-bit pixels, d[31:24]=a, d[23:16]=b, d[15:8]=g, d[7:0]=r).
 
 Optional properties:
-- clocks : List of clocks used by the framebuffer. Clocks listed here
-           are expected to already be configured correctly. The OS must
-           ensure these clocks are not modified or disabled while the
-           simple framebuffer remains active.
+- clocks : List of clocks used by the framebuffer.
+- *-supply : Any number of regulators used by the framebuffer. These should
+	     be named according to the names in the device's design.
+
+  The above resources are expected to already be configured correctly.
+  The OS must ensure they are not modified or disabled while the simple
+  framebuffer remains active.
+
 - display : phandle pointing to the primary display hardware node
 
 Example:
···
 		stride = <(1600 * 2)>;
 		format = "r5g6b5";
 		clocks = <&ahb_gates 36>, <&ahb_gates 43>, <&ahb_gates 44>;
+		lcd-supply = <&reg_dc1sw>;
 		display = <&lcdc0>;
 	};
 	stdout-path = "display0";