dmaengine: imx-sdma: Add i.MX7 support

Allow i.MX7 to work with the imx-sdma driver.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Tested-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>