msm_fb: display: add sysfs and clock control to smart panel

Both vsync enabled and disabled are controlled by framework
through ioctl. Driver reports vsync event to framework via
sysfs. Meanwhile, mdp related clocks are enabled by frame
work at vsync enabled request and disabled by driver if there
is no any display update within specifid vsync period.

Change-Id: Ice5be3a6db5930b95bdd2f718d9256bf73936e23
Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>
(cherry picked from commit 3c406e4eec79b710b7f5b5b67c23db7af871be40)