usb: musb: hsdma: change back to use musb_read/writew

Blackfin platform doesn't support 32bits musbdma registers, so change back to
use musb_read/writew instead of musb_read/writel and simply some format casts.

Signed-off-by: Bob Liu <lliubbo@gmail.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>