ASoC: rsnd: add missing .irq callback for DMA

commit b5b442ab ("ASoC: rsnd: add .irq callback") added .irq callback
but SSI DMA is missing it. This patch adds it.

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