drm/amd/display: Fix underflow when setting underscan on DCN401

[WHY & HOW]
When underscan is set through xrandr, it causes the stream destination
rect to change in a way it becomes complicated to handle the calculations
for subvp. Since this is a corner case, disable subvp when underscan is
set.

Fix the existing check that is supposed to catch this corner case by
adding a check based on the parameters in the stream

Cc: Mario Limonciello <mario.limonciello@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Reviewed-by: Dillon Varone <dillon.varone@amd.com>
Reviewed-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>