drm/amd/display: Revert check for phantom BPP

[Description]
Revert change since enabling SubVP on 8K60 single cable
results in corruption

Reviewed-by: Nevenko Stupar <Nevenko.Stupar@amd.com>
Reviewed-by: Martin Leung <Martin.Leung@amd.com>
Acked-by: Brian Chang <Brian.Chang@amd.com>
Signed-off-by: Alvin Lee <Alvin.Lee2@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>