msm: camera: cpas: Remove duplicate code and add unlock mutex

This change removes duplicate code that was introduced as part
of the driver upgrade port from msm-4.9 branch. It also adds
unlock mutex that was omitted by the same upgrade.

Change-Id: Idc86129fd1510d6a0de2986447465f30d4096054
Signed-off-by: Venkat Chinta <vchinta@codeaurora.org>