msm: mdss: Fix mem leak during WFD session

WFD Buffers are not getting freed as the WRITEBACK
TERMINATE ioctl is returning early. Remove early
return such that writeback terminate executes and
free the buffers.

Change-Id: I1d5b419ad2dcf863ade1be21c0fbe7d944317005
Signed-off-by: Jayant Shekhar <jshekhar@codeaurora.org>