usb: gadget: udc: renesas_usb3: add support for dedicated DMAC

The USB3.0 peripheral controller on R-Car SoCs has a dedicated DMAC.
The DMAC needs a "PRD table" in system memory and the DMAC can have
four PRD tables. This patch adds support for the DMAC.
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>