msm: camera: reqmgr: Fix mutex unlock issue

In case of errors, releasing mutex of a link
without acquire the mutex leads to device crash.
Fix mutex locking issues.

Change-Id: I61fba878016528d7761d5e90e8bf2301a3187a25
Signed-off-by: Suresh Vankadara <svankada@codeaurora.org>