dt-bindings: pinctrl: renesas: Drop unneeded quotes

Drop unneeded quotes over simple string values to fix a soon to be
enabled yamllint warning:

  [error] string value is redundantly quoted with any quotes (quoted-strings)
Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20231122224409.2808999-1-robh@kernel.orgSigned-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Documentation/devicetree/bindings/pinctrl/renesas,rza2-pinctrl.yaml

@@ -20,7 +20,7 @@ description:
 
 properties:
   compatible:
-    const: "renesas,r7s9210-pinctrl" # RZ/A2M
+    const: renesas,r7s9210-pinctrl # RZ/A2M
 
   reg:
     maxItems: 1