dmaengine: omap-dma: Add memory barrier to dma_resume path

Add mb() call to resume path to ensure the necessary barrier.
Resume can happen after waking up from suspend for example.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>