drm/amd/display: misc for dio encoder refactor

drm/amd/display: misc for dio encoder refactor

[WHY]
These are left required changes for dio encoder refactor.

[HOW]
1. original logic is separated by config option
2. new link encoder dp enable/disable code for dcn35
3. process fec only for DP 8b10b encoding

Reviewed-by: Cruise Hung <cruise.hung@amd.com>
Signed-off-by: Peichen Huang <PeiChen.Huang@amd.com>
Signed-off-by: Wayne Lin <wayne.lin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>