msm: mdss: release the mutex on rotator kickoff failure

Rotator shared lock is released on the rotator completion, but when
rotator kickoff fails as completion wont happen lock is not released.
Handle the failure case gracefully.

Change-Id: I2973a1eec617b36c7af8e7c3f250baefe9f245cf
Signed-off-by: Kalyan Thota <kalyant@codeaurora.org>
Signed-off-by: Bharat Pawar <bpawar@codeaurora.org>
Signed-off-by: Nirmal Abraham <nabrah@codeaurora.org>