dmaengine: zynqmp_dma: Fix issues with overflow interrupt

This patch fixes the below issues.
--> Need to clear the channel data count register
when overflow interrupts occurs.
--> Reduce the log level from _info to _dbg when
overflow interrupt occurs.

Signed-off-by: Kedareswara rao Appana <appanad@xilinx.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>