ARM: common: edma: clear completion interrupts on stop

When stopping a DMA transfer with interrupts disabled it is possible
that the DMA transfer completes before the events are cleared. In
this case the completion interrupt will be pending, causing a
completion callback after the transfer was stopped.

By clearing the completion interrupt for the stopping channel it is
ensured that no completion event will be generated after the stop.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Acked-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>