usb: renesas_usbhs: standardize d{0,1}fifo control

To expand DnFIFOs in the future, this patch standardizes the d{0,1}fifo
control using new macros.

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