dmaengine: fsl-edma: add edma version and configurable registers

This patch adds configurable registers (using __iomem addresses)
to allow the use of fsl-edma-common code with slightly different
edma module versions, as Vybrid (v1) and ColdFire (v2) are.

Signed-off-by: Angelo Dureghello <angelo@sysam.it>
Tested-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>