ASoC: msm8x16: configure mux and gpio to enable mclk

The loopback mixer control at present does not
configure the mux and gpio before enabling the mclk.
So, the mclk is not supplied to the codec. Configure
the mux and gpio so that mclk is supplied correctly.
Also, acquire a mutex lock before enabling afe digital
core clock.

Change-Id: If298fdc9784b1fc47554dc3e56cbd7957ecd7d2d
Signed-off-by: Aravind Kumar <akumark@codeaurora.org>