drm/amd/display: Fix eDP Black screen after S4 resume

[Why]
Power down of PHY on eDP requires us to call eDP power
control to power on again

[How]
1. In the case link rates don't match, disable PHY
requires calling of eDP power control ON after

2. Link disable case limit to eDP path since
this is not really applicable to DP since we do
power down PHY as part of verify link cap

3. Move detection of eDP link settings to be
done even for S4 resume cases where other
dpcd cap read and edid read can be skipped

Signed-off-by: Anthony Koo <Anthony.Koo@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>