ASoC: wcd9xxx: don't acquire BCL from codec driver

Codec driver shouldn't acquire BCL lock especially from DAPM widget.
Otherwise mutex deadlock can happen in below scenario.
--
thread0                         | thread1
                                | *lock BCL
                                | power up DAPM widget B
                                |         snd_soc_dapm_sync()
DAPM widget A starts sync       |
*lock BCL                       |
--

Fix codec driver to hold codec->mutex instead of BCL and prevent possible
mutex deadlock.

CRs-fixed: 502427
Change-Id: Ibc4a70eba4824a384874244f36831e2d98c85d4b
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>