msm: display: pp: histogram collection for mdss

MSMFB_HISTOGRAM_START, MSMFB_HISTOGRAM_STOP and MSMFB_HISTOGRAM support
Only read the histogram data when there is a new display commit
Only generate the next histogram collection when there is a display commit
Cache the histogram data in order to respond quickly

Change-Id: I4532eca3bb8daa9e03ef78770c9e47d968c7c140
Signed-off-by: Ken Zhang <kenz@codeaurora.org>
8 files changed