usb: renesas_usbhs: fixup DMA transport data alignment

renesas_usbhs dma can transport 8byte alignment data, not 4byte.
This patch fixup it.

Reported-by: Sugnan Prabhu S <sugnan.prabhu@renesasmobile.com>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>