dt-bindings: pinctrl: ocelot: Add ServalT SoC support

Add the documentation for the Microsemi ServalT pinmuxing and gpio
controller.
Signed-off-by: NHoratiu Vultur <horatiu.vultur@microchip.com>
Link: https://lore.kernel.org/r/20220125131858.309237-2-horatiu.vultur@microchip.comSigned-off-by: NLinus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/pinctrl/mscc,ocelot-pinctrl.txt

@@ -4,8 +4,8 @@ Microsemi Ocelot pin controller Device Tree Bindings
 Required properties:
  - compatible		: Should be "mscc,ocelot-pinctrl",
 			  "mscc,jaguar2-pinctrl", "microchip,sparx5-pinctrl",
-			  "mscc,luton-pinctrl", "mscc,serval-pinctrl" or
-			  "microchip,lan966x-pinctrl"
+			  "mscc,luton-pinctrl", "mscc,serval-pinctrl",
+			  "microchip,lan966x-pinctrl" or "mscc,servalt-pinctrl"
  - reg			: Address and length of the register set for the device
  - gpio-controller	: Indicates this device is a GPIO controller
  - #gpio-cells		: Must be 2.