dmaengine: at_hdmac: remove clear-on-read in atc_dostart()

dmaengine: at_hdmac: remove clear-on-read in atc_dostart()

commit ed8b0d67f33518a16c6b2450fe5ebebf180c2d04 upstream.

This loop on EBCISR register was designed to clear IRQ sources before enabling
a DMA channel. This register is clear-on-read so a race condition can appear if
another channel is already active and has just finished its transfer.
Removing this read on EBCISR is fixing the issue as there is no case where an IRQ
could be pending: we already make sure that this register is drained at probe()
time and during resume.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>