drm/amd/display: retry LT on failing LT in automated request

[Description]
Link training is not retried in automated link training request.
In case link training is occasionally failing, there is not way to retry
so the requested lane settings will not set.

Signed-off-by: Wenjing Liu <Wenjing.Liu@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>