FE state is SND_SOC_DPCM_STATE_PREPARE now, BE1 is
used by FE.

Later when new BE2 is added to FE by mixer update,
it will call dpcm_run_update_startup() to update
BE2's state, but unfortunately BE2 .prepare() meets
error, it will disconnect all non started BE.

This make BE1 dai skip .hw_free() and .shutdown(),
and the BE1 users will never decrease to zero.
Signed-off-by: zhucancan <zhucancan@vivo.com>
Link: https://lore.kernel.org/r/ALMAWwB5CP9aAcKXCU5FzqqF.1.1590747164172.Hmail.zhucancan@vivo.comSigned-off-by: Mark Brown <broonie@kernel.org>