msm_fb: display: add pipe commit ioctl

currently, pan display serves as pipe commit. However it
may spend long time pending on cosole_lock() which cause
flickering on HDMI. Add pipe commit ioctl to allow commit
from overlay in addition to pan_display.

CRs-fixed: 391564
Change-Id: I163b5d96f727b70b4d5693e9a414b59339818998
Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>