ASoC: wcd-mbhc: Check if mutex is locked before mutex destroy

Mutex destroy is called as part of wcd_mbhc_deinit during SSR
for hph pa lock when lock is taken resulting in warning. Check
if mutex is locked and unlock mutex before destroy so as to
remove warning.

Change-Id: I521903f9ab24222278d6fb3f349da18c98131c60
Signed-off-by: Vatsal Bucha <vbucha@codeaurora.org>