drm/msm/sde: fix to unlock mutex on early wakeup

This change unlocks the resource lock mutex while bailing
out on early wakeup event when auto refresh is enabled.

Change-Id: I544e6a2037a4d37d33c37beb5f015916e19c2695
Signed-off-by: Jeykumar Sankaran <jsanka@codeaurora.org>