msm_fb: display: free base layer pipe at adb stop

Base layer pipe need to be freed at adb stop so that same
pipe can be allocated at adb start.

CRs-fixed: 390644
Change-Id: I948bb27687cfe1c96cc3b071b7bb9bb84b2c52c6
Signed-off-by: Kalyan Thota <kalyant@codeaurora.org>
Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>