usb: renesas_usbhs: Change USBHS_TYPE_R8A779x to USBHS_TYPE_RCAR_GEN2

Since the HSUSB controllers of R-Car Gen2 are the same specification
(they have 16 pipes and usb-dmac), this patch changes USBHS_TYPE_R8A7790
and USBHS_TYPE_R8A7791 to USBHS_TYPE_RCAR_GEN2.

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