commit 46389470 deleted redundant
chan_id and chancnt initialization in dma drivers as this is done
in dma_async_device_register().

However, atc_enable_irq() relied on chan_id set before registering
the device, what left only channel 0 functional for this driver.

This patch introduces atc_enable/disable_chan_irq() as a variant
of atc_enable/disable_irq() with the channel as explicit argument.
Signed-off-by: NNikolaus Voss <n.voss@weinmann.de>
Signed-off-by: NNicolas Ferre <nicolas.ferre@atmel.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: NVinod Koul <vinod.koul@linux.intel.com>