dt-bindings: pinctrl: mt7988: fix some node-names to have pins at end

left warnings:
Documentation/devicetree/bindings/pinctrl/mediatek,mt7988-pinctrl.example.dtb: pinctrl@1001f000: mdio0-pins:conf: 'groups' does not match any of the regexes: 'pinctrl-[0-9]+'
	from schema $id: http://devicetree.org/schemas/pinctrl/mediatek,mt7988-pinctrl.yaml#
Documentation/devicetree/bindings/pinctrl/mediatek,mt7988-pinctrl.example.dtb: pinctrl@1001f000: mdio0-pins:conf: 'pins' is a required property
	from schema $id: http://devicetree.org/schemas/pinctrl/mediatek,mt7988-pinctrl.yaml#

Author: frank-w

Documentation/devicetree/bindings/pinctrl/mediatek,mt7988-pinctrl.yaml

@@ -501,7 +501,7 @@ examples:
         interrupt-parent = <&gic>;
         #interrupt-cells = <2>;
 
-        i2c0_pins: i2c0-pins-g0 {
+        i2c0_pins: i2c0-g0-pins {
           mux {
             function = "i2c";
             groups = "i2c0_1";
@@ -520,14 +520,14 @@ examples:
           };
         };
 
-        mmc0_pins_emmc_51: mmc0-pins-emmc-51 {
+        mmc0_pins_emmc_51: mmc0-emmc-51-pins {
           mux {
             function = "flash";
             groups = "emmc_51";
           };
         };
 
-        mmc0_pins_sdcard: mmc0-pins-sdcard {
+        mmc0_pins_sdcard: mmc0-sdcard-pins {
           mux {
             function = "flash";
             groups = "sdcard";