drm/amd/display: Maintain current link settings in link loss interrupt

[Why]
DP compliance test case 400.3.2.3 is failed because in link loss interrupt
the current link settings is not used in the DP link training.

[How]
In link loss interrupt, use the current link settings in the following DP
link training.

Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Gary Li <garyli12@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>