drm/amdgpu: remove non-DC DCE 11 code
DC has been the default for ~8 years now and supports
many things that the non-DC code does not (audio, DP MST, etc.).
No DCE 11.x IPs ever supported analog encoders so that is not
an issue. Finally drop this code.
Acked-by: Timur Kristóf <timur.kristof@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>