msm: mdss: Support scalar programming for all usecases

Program scalar registers for both RGB and VIG pipes
when requested by the user. The scalar factors are
also computed by the user.

Change-Id: I6854a9ff3acdef07bb6a964f2f3686612230eff3
Signed-off-by: Sree Sesha Aravind Vadrevu <svadrevu@codeaurora.org>