ARM: edma: Add edma_assign_channel_eventq() to move channel to a give queue

In some cases it is desired to move a channel to a specific event queue.
Such a use case is audio, where it is preferred that it is served with
highest priority compared to other DMA clients.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>