dmaengine: edma: Simplify the interrupt handling

With the merger of the arch/arm/common/edma.c code into the dmaengine
driver, there is no longer need to have per channel callback/data storage
for interrupt events.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>