drm/amd/display: Remove connect DIG FE to its BE during timing programming

[why]
Causes regression with MST DSC displays not lighting up after DPMS

[how]
Revert commit 8cc426d7 ("drm/amd/display: Program DSC during timing programming")

Signed-off-by: Nikola Cornij <nikola.cornij@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>