dmaengine: ti: edma: Clean up the 2x32bit array register accesses

Introduce defines for getting the array index and the bit number within the
64bit array register pairs.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20190716082655.1620-2-peter.ujfalusi@ti.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>