drm/amd/display: Fix DSC force enable on SST

[why]
Previously when force enabling DSC on SST display we unknowingly
supressed lane count, which caused DSC to be enabled automatically.

[how]
By adding an additional flag to force enable DSC in dc_dsc.c DSC can
always be enabled with debugfs dsc_clock_en forced to 1

Cc: stable@vger.kernel.org
Signed-off-by: Eryk Brol <eryk.brol@amd.com>
Signed-off-by: Mikita Lipski <mikita.lipski@amd.com>
Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>