dt-bindings: pinctrl: sh-pfc: Document r8a77961 support

Add DT binding documentation for the Pin Function Controller in the
Renesas R-Car M3-W+ (R8A77961) SoC.

Update all references to R-Car M3-W from "r8a7796" to "r8a77960", to
avoid confusion between R-Car M3-W (R8A77960) and M3-W+.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20191023122955.12420-2-geert+renesas@glider.be

Documentation/devicetree/bindings/pinctrl/renesas,pfc-pinctrl.txt

@@ -28,7 +28,8 @@ Required Properties:
     - "renesas,pfc-r8a7793": for R8A7793 (R-Car M2-N) compatible pin-controller.
     - "renesas,pfc-r8a7794": for R8A7794 (R-Car E2) compatible pin-controller.
     - "renesas,pfc-r8a7795": for R8A7795 (R-Car H3) compatible pin-controller.
-    - "renesas,pfc-r8a7796": for R8A7796 (R-Car M3-W) compatible pin-controller.
+    - "renesas,pfc-r8a7796": for R8A77960 (R-Car M3-W) compatible pin-controller.
+    - "renesas,pfc-r8a77961": for R8A77961 (R-Car M3-W+) compatible pin-controller.
     - "renesas,pfc-r8a77965": for R8A77965 (R-Car M3-N) compatible pin-controller.
     - "renesas,pfc-r8a77970": for R8A77970 (R-Car V3M) compatible pin-controller.
     - "renesas,pfc-r8a77980": for R8A77980 (R-Car V3H) compatible pin-controller.