dt-bindings: pinctrl: marvell,armada3710-xb-pinctrl: add missing items keyword

dt-bindings: pinctrl: marvell,armada3710-xb-pinctrl: add missing items keyword

Even though the type of the 'groups' property of a pinmux node is
specified as string-array in pinmux-node.yaml, but trying to use
multiple strings causes dtbs_check warnings.

For example, checking the following dts ...

  $ cat arch/arm64/boot/dts/marvell/armada-3720-test.dts
  /dts-v1/;

  #include "armada-372x.dtsi"

  &pinctrl_nb {
          pwm-gpio-pins {
                  groups = "pwm0", "pwm1", "pwm2", "pwm3";
                  function = "gpio";
          };
  };

... results in this warning:

  arch/arm64/boot/dts/marvell/armada-3720-test.dtb: pinctrl@13800 (marvell,armada3710-nb-pinctrl): pwm-gpio-pins:groups: ['pwm0', 'pwm1', 'pwm2', 'pwm3'] is too long
	  from schema $id: http://devicetree.org/schemas/pinctrl/marvell,armada3710-xb-pinctrl.yaml

Add the missing 'items' keyword to the schema to allow using multiple
strings without such warnings. Also adjust the indentation of the next
statements accordingly.

Signed-off-by: Gabor Juhos <j4g8y7@gmail.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Fixes: c1c9641a04e83 ("dt-bindings: pinctrl: Convert marvell,armada-3710-(sb|nb)-pinctrl to DT schema")
Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>