usb: gadget: udc: renesas_usb3: add support for R-Car M3-W

This patch adds support for R-Car M3-W. This patch also adds R-Car
Gen3 generic version's compatible and changes ".compatible" in
the usb3_of_match from "renesas,r8a7796-usb3-peri" to
"renesas,rcar-gen3-usb3-peri".

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>