drm/amd/display: Check context constructed for pipe split flags is still valid

[WHY?]
After applying pipesplit flags, DML can select a different configuration upon
revalidation, despite the desired one still being valid.

[HOW?]
Check the configuration is still has mode support, and apply it.

Reviewed-by: Martin Leung <Martin.Leung@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Dillon Varone <Dillon.Varone@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>