usb: gadget: udc: renesas_usb3: fix Pn_RAMMAP.Pn_MPKT value

According to the datasheet of R-Car Gen3, the Pn_RAMMAP.Pn_MPKT should
be set to one of 8, 16, 32, 64, 512 and 1024. Otherwise, when a gadget
driver uses an interrupt endpoint, unexpected behavior happens. So,
this patch fixes it.

Fixes: 746bfe63 ("usb: gadget: renesas_usb3: add support for Renesas USB3.0 peripheral controller")
Cc: <stable@vger.kernel.org> # v4.5+
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>