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

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.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>