usb: gadget: udc: renesas_usb3: add support for r8a77990

Since r8a77990 (R-Car E3) doesn't have VBUS detect pin and
number of ramif is 4, this patch adds a new renesas_usb3_priv
variable for the SoC.

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