pinctrl: mediatek: Modify pinctrl bindings for mt6397.

Since 6397 is no need to support interrupt controller,
moving interrupt controller relate property to optional list.
Also adding mt8173 and mt8127 to bindings.
Signed-off-by: Hongzhou Yang <hongzhou.yang@mediatek.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/pinctrl/pinctrl-mt65xx.txt

@@ -3,9 +3,11 @@
 The Mediatek's Pin controller is used to control SoC pins.
 
 Required properties:
-- compatible: value should be either of the following.
+- compatible: value should be one of the following.
     (a) "mediatek,mt8135-pinctrl", compatible with mt8135 pinctrl.
-- mediatek,pctl-regmap: Should be a phandle of the syscfg node.
+    (b) "mediatek,mt8173-pinctrl", compatible with mt8173 pinctrl.
+    (c) "mediatek,mt6397-pinctrl", compatible with mt6397 pinctrl.
+    (d) "mediatek,mt8127-pinctrl", compatible with mt8127 pinctrl.
 - pins-are-numbered: Specify the subnodes are using numbered pinmux to
   specify pins.
 - gpio-controller : Marks the device node as a gpio controller.
@@ -24,6 +26,9 @@ Required properties:
             Only the following flags are supported:
             0 - GPIO_ACTIVE_HIGH
             1 - GPIO_ACTIVE_LOW
+
+Optional properties:
+- mediatek,pctl-regmap: Should be a phandle of the syscfg node.
 - reg: physicall address base for EINT registers
 - interrupt-controller: Marks the device node as an interrupt controller
 - #interrupt-cells: Should be two.