video: msm: Add user-defined backlight scaling

Add method for scaling backlight based off of a user provided ratio and
minimum level for the scaling to be applied.

Change-Id: I494bdd4545e9e02602faa01bed820120cd96298f
Signed-off-by: Carl Vanderlip <carlv@codeaurora.org>
(cherry picked from commit f0fd8e7323ea0f60539918528a4cfa1edb39b828)
lge: display: add CONFIG_FB_MSM_NO_MDP_PIPE_CTRL