drm/msm/sde: Add backlight class support for sde drm driver

Add backlight class support for sde drm driver which provides
sysfs interface to userspace to control display brightness.

Change-Id: I4f777618e8f2ff61e72beddb7a5bd1fa6e9dd5df
Signed-off-by: Vishnuvardhan Prodduturi <vproddut@codeaurora.org>
11 files changed