ASoC: rsnd: ignore DIRQ when DMA transfer

SSI interrupt handler of R-Car sound driver will be called
when DIRQ (= Data read/write timing for PIO) or
UIRQ / OIRQ (= under/over run error).
DIRQ "interrupt" doesn't occur when DMA transfer, but then,
DIRQ "status bit" might occur. we need to ignore this DIRQ
operation when DMA. Otherwise, driver will push/pop as PIO.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>