ASoC: dpcm: fix BE dai not hw_free and shutdown

In case, one BE is used by two FE1/FE2
FE1--->BE-->
       |
FE2----]
when FE1/FE2 call dpcm_be_dai_hw_free() together
the BE users will be 2 (> 1), hence cannot be hw_free
the be state will leave at, ex. SND_SOC_DPCM_STATE_STOP

later FE1/FE2 call dpcm_be_dai_shutdown(),
will be skip due to wrong state.
leaving the BE not being hw_free and shutdown.

The BE dai will be hw_free later when calling
dpcm_be_dai_shutdown() if still in invalid state.

Signed-off-by: KaiChieh Chuang <kaichieh.chuang@mediatek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>