drm/amd/display: fix odm scaling

There are two issues with scaling calculations, odm recout
calculation and matching viewport to actual recout.

This change fixes both issues. Odm recout calculation via
special casing and viewport matching issue by reworking
the viewport calcualtion to use scaling ratios and recout
to derrive the required offset and size.

Signed-off-by: Dmytro Laktyushkin <Dmytro.Laktyushkin@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>