drm/amd/display: Fix DVI-D/HDMI adapters

drm/amd/display: Fix DVI-D/HDMI adapters

When the EDID has the HDMI bit, we should simply select
the HDMI signal type even on DVI ports.

For reference see, the legacy amdgpu display code:
amdgpu_atombios_encoder_get_encoder_mode
which selects ATOM_ENCODER_MODE_HDMI for the same case.

This commit fixes DVI connectors to work with DVI-D/HDMI
adapters so that they can now produce output over these
connectors for HDMI monitors with higher bandwidth modes.
With this change, even HDMI audio works through DVI.

For testing, I used a CAA-DMDHFD3 DVI-D/HDMI adapter
with the following GPUs:

Tahiti (DCE 6) - DC can now output 4K 30 Hz over DVI
Polaris 10 (DCE 11.2) - DC can now output 4K 60 Hz over DVI

Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>