drm/amd/display: DP Compliance 400.1.1 failure

drm/amd/display: DP Compliance 400.1.1 failure

[Why]
400.1.1 is failing because we are not performing link training when
we get an HPD pulse for the same display. This is breaking DP
compliance

[How]
Always perform link training after HPD pulse if the detection
reason is not  DETECT_REASON_HPDRX.

Signed-off-by: abdoulaye berthe <abdoulaye.berthe@amd.com>
Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>