Pause and resume controls are useful for audio devices. This also returns
correct status from atc_tx_status() in case chan is paused.

Idea from dw_dmac patch by Linus Walleij.
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>