msm_fb: Release semaphore when display Unblank fails

When continuous splash is enabled, the display subsystem will be
turned on during first pan display after boot up. During this
process, we acquire a semaphore. Release the semaphore if display
init fails and the function has to return early.

CRs-fixed: 441973
Change-Id: I4c8ba0b5e7710a6f3d409be619d5014b3ee32e5b
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>