dt-bindings: pinctrl: toshiba,visconti: Fix number of items in groups

The "groups" property can hold multiple entries (e.g.
toshiba/tmpv7708-rm-mbrc.dts file), so allow that by dropping incorrect
type (pinmux-node.yaml schema already defines that as string-array) and
adding constraints for items. This fixes dtbs_check warnings like:

toshiba/tmpv7708-rm-mbrc.dtb: pinctrl@24190000 (toshiba,tmpv7708-pinctrl):
pwm-pins:groups: ['pwm0_gpio16_grp', 'pwm1_gpio17_grp', 'pwm2_gpio18_grp', 'pwm3_gpio19_grp'] is too long

Fixes: 1825c1fe0057 ("pinctrl: Add DT bindings for Toshiba Visconti TMPV7700 SoC")
Cc: [e-mail]
Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Acked-by: Conor Dooley <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

Documentation/devicetree/bindings/pinctrl/toshiba,visconti-pinctrl.yaml

···
       groups:
         description:
           Name of the pin group to use for the functions.
-        $ref: /schemas/types.yaml#/definitions/string
-        enum: [i2c0_grp, i2c1_grp, i2c2_grp, i2c3_grp, i2c4_grp,
-               i2c5_grp, i2c6_grp, i2c7_grp, i2c8_grp,
-               spi0_grp, spi0_cs0_grp, spi0_cs1_grp, spi0_cs2_grp,
-               spi1_grp, spi2_grp, spi3_grp, spi4_grp, spi5_grp, spi6_grp,
-               uart0_grp, uart1_grp, uart2_grp, uart3_grp,
-               pwm0_gpio4_grp, pwm0_gpio8_grp, pwm0_gpio12_grp,
-               pwm0_gpio16_grp, pwm1_gpio5_grp, pwm1_gpio9_grp,
-               pwm1_gpio13_grp, pwm1_gpio17_grp, pwm2_gpio6_grp,
-               pwm2_gpio10_grp, pwm2_gpio14_grp, pwm2_gpio18_grp,
-               pwm3_gpio7_grp, pwm3_gpio11_grp, pwm3_gpio15_grp,
-               pwm3_gpio19_grp, pcmif_out_grp, pcmif_in_grp]
+        items:
+          enum: [i2c0_grp, i2c1_grp, i2c2_grp, i2c3_grp, i2c4_grp,
+                 i2c5_grp, i2c6_grp, i2c7_grp, i2c8_grp,
+                 spi0_grp, spi0_cs0_grp, spi0_cs1_grp, spi0_cs2_grp,
+                 spi1_grp, spi2_grp, spi3_grp, spi4_grp, spi5_grp, spi6_grp,
+                 uart0_grp, uart1_grp, uart2_grp, uart3_grp,
+                 pwm0_gpio4_grp, pwm0_gpio8_grp, pwm0_gpio12_grp,
+                 pwm0_gpio16_grp, pwm1_gpio5_grp, pwm1_gpio9_grp,
+                 pwm1_gpio13_grp, pwm1_gpio17_grp, pwm2_gpio6_grp,
+                 pwm2_gpio10_grp, pwm2_gpio14_grp, pwm2_gpio18_grp,
+                 pwm3_gpio7_grp, pwm3_gpio11_grp, pwm3_gpio15_grp,
+                 pwm3_gpio19_grp, pcmif_out_grp, pcmif_in_grp]
+        minItems: 1
+        maxItems: 8
 
       drive-strength:
         enum: [2, 4, 6, 8, 16, 24, 32]