drm/msm/dsi-staging: add dsi panel driver

Add dsi panel driver to parse and set panel configurations
like horizontal and vertical settings, configure regulators,
gpios and clocks. Add panel on/off, suspend/resume and panel
commands transmission logic.

Change-Id: I12044e4f9f2640f9e8bbc7aca8d7a5d9ec92944b
Signed-off-by: Ajay Singh Parmar <aparmar@codeaurora.org>