dt-bindings: clock: renesas: rcar-usb2-clock-sel: Add r8a77961 support

This patch adds support for r8a77961 (R-Car M3-W+).

To avoid confusion between R-Car M3-W (R8A77960) and R-Car M3-W+
(R8A77961), this patch also updates the comment of
"renesas,r8a7796-rcar-usb2-clock-sel".
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Link: https://lore.kernel.org/r/1585200608-30103-1-git-send-email-yoshihiro.shimoda.uh@renesas.comSigned-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Documentation/devicetree/bindings/clock/renesas,rcar-usb2-clock-sel.txt

@@ -27,7 +27,9 @@ Required properties:
 - compatible: "renesas,r8a7795-rcar-usb2-clock-sel" if the device is a part of
 	      an R8A7795 SoC.
 	      "renesas,r8a7796-rcar-usb2-clock-sel" if the device if a part of
-	      an R8A7796 SoC.
+	      an R8A77960 SoC.
+	      "renesas,r8a77961-rcar-usb2-clock-sel" if the device if a part of
+	      an R8A77961 SoC.
 	      "renesas,rcar-gen3-usb2-clock-sel" for a generic R-Car Gen3
 	      compatible device.