drm/amd/display: upgrade scaler math

This change will allow the viewport overlap to apply to rotated/
mirrored surfaces. Viewport overlap results in extra pixels being
added to viewport allowing the first few pixels to be scaled as
if there is no cut-off(mpo or pipe split) and allows us to get matching
crc's between scaled split and unsplit outputs of the same thing.

Signed-off-by: Dmytro Laktyushkin <Dmytro.Laktyushkin@amd.com>
Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>