Revert "drm/amd/display: Fix underscan not using proper scaling"

This reverts commit 80e80ec8.

This commit fixed an issue with underscan commits not updating all
needed timing values, but through various refactors it is no longer
necessary. It causes corruption on odm combine by
overwriting the halved h_active in the stream timing

Signed-off-by: David Francis <David.Francis@amd.com>
Reviewed-by: Roman Li <Roman.Li@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>