dma: imx-dma: retrieve MEM and IRQ from resources

Retrieve MEM and IRQ from resources rather than directly using the
value by including machine header.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@linux.intel.com>