ASoC: rsrc-card: enable multi cpu/codec for DPCM

Current rsrc-card is assuming 1 FE (= CPU), 1 BE (= codec) on card.
But, it will support multi FE/BE card. This is prepare for it.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Tested-by: Keita Kobayashi <keita.kobayashi.ym@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>