power: msm-core: Fix mutex not getting unlocked in error path

When this copy_to_user() fails, the mutex won't be unlocked. Fix it.

Change-Id: Ide7a7ed9ca8a8d33dafd2060a0c24c57e6396ea8
Signed-off-by: Sultanxda <sultanxda@gmail.com>
Signed-off-by: Simao Gomes Viana <xdevs23@outlook.com>