drm/amd/display: Add w/a to reset PHY before link training in verify_link_cap

[Why]
PHY will sometimes be in bad state on hotplugging display from USB-C
dongle.

[How]
Add additional calls to disable and then enable PHY before link training
starts during verify_link_cap.

Signed-off-by: George Shen <george.shen@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>