msm_fb : display : Block RGB downscale in MDP 4.0 and 4.1

Downscale is not allowed on RGB pipes in MDP 4.0 and 4.1. Hence,
fail the OVERLAY_SET ioctl for such configurations.

Signed-off-by: Pradeep Jilagam <pjilagam@codeaurora.org>
(cherry picked from commit 3545573720822ce97ec37586f10fdf74a6d4f090)

Change-Id: I8445c18ac21cb7322eb9eb4c802623df5da07eb7
Signed-off-by: Gopal Goberu <ggober@codeaurora.org>