drm/amd/display: Only use analog link encoder with analog engine

drm/amd/display: Only use analog link encoder with analog engine

Some GPUs have analog connectors that work with a DP bridge chip
and don't actually have an internal DAC: Those should not use
the analog link encoder code path.

Fixes: 0fbe321a93ce ("drm/amd/display: Implement DCE analog link encoders (v2)")
Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>