drm/msm/dsi-staging: add support for checking panel status

Panel health status can be read back from panel using DCS read
mechanism. This change adds support for the same along with
fixing various HW configuration issues related with read back
from MIPI peripherals.

Change-Id: I129f5c564dd4e4acda56031dc2f985267ee1a590
Signed-off-by: Sandeep Panda <spanda@codeaurora.org>