dma:mmp_tdma: get sram pool through device tree

    Support to get sram pool from generic device tree binding. The
existing way of get sram poll, directly call sram_get_gpool(), still
work here.

Signed-off-by: Nenghua Cao <nhcao@marvell.com>
Acked-by: Zhangfei Gao <zhangfei.gao@gmail.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>