ASoC: rsnd: use mod base common method on SSIU

ASoC: rsnd: use mod base common method on SSIU

Renesas sound needs many devices
(SSI/SSIU/SRC/CTU/MIX/DVC/CMD/AudioDMAC/AudioDMACpp).
SSI/SRC/CTU/MIX/DVC are implemented as module.
SSI parent, SSIU are implemented as part of SSI
CMD is implemented as part of CTU/MIX/DVC
AudioDMAC/AudioDMACpp are implemented as part of SSI/SRC
It is nice sense that these all devices are implemented as mod.

This patch makes SSIU mod base common method

Signed-off-by: Kuninori Morimoto <[email protected]>
Signed-off-by: Mark Brown <[email protected]>