USB-musb: move to dma_transfer_direction

fixup usage of dma direction by introducing dma_transfer_direction,
this patch moves usb/musb driver to use new enum

Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Acked-by: Felipe Balbi <balbi@ti.com>
Acked-by: Mian Yousaf Kaukab <mian.yousaf.kaukab@stericsson.com>