msm: mdss: Adding interface for supporting destination scaler.

MSM mdss 3xx  hardware supports destination scaling for upscaling the
layer mixer output to the panel resolution. This change adds the new
interface to support the user space client using this feature.

CRs-Fixed: 988990
Change-Id: Ie267f0fd81cd8cf04a5c1f1c6a8c48d456a3035e
Signed-off-by: Benjamin Chan <bkchan@codeaurora.org>
Signed-off-by: Naseer Ahmed <naseer@codeaurora.org>