usb: gadget: renesas_usbhs: fix compile warning

| drivers/usb/renesas_usbhs/fifo.c: In function ‘usbhsf_dma_prepare_push’:
| drivers/usb/renesas_usbhs/fifo.c:823:7: warning: cast from pointer \
	to integer of different size [-Wpointer-to-int-cast]
| drivers/usb/renesas_usbhs/fifo.c: In function ‘usbhsf_dma_try_pop’:
| drivers/usb/renesas_usbhs/fifo.c:900:7: warning: cast from pointer \
	to integer of different size [-Wpointer-to-int-cast]

Signed-off-by: Felipe Balbi <balbi@ti.com>