dma: imx-sdma: Add new dma type for ssi dual fifo script

This patch adds a new DMA_TYPE for SSI dual FIFO script, included
in SDMA firmware version 2. This script would allow SSI use dual
fifo mode to transimit/receive data without occasional hardware
underrun/overrun.

Signed-off-by: Nicolin Chen <b42378@freescale.com>
Acked-by: Kumar Gala <galak@codeaurora.org>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>