drm/amd/display: remove unhelpful 5ms delay

[Why]
Scaler vendor confirmed the 5ms was not helpful so no point in keeping
it.

[How]
Revert 5ms delay after setting training pattern.

Signed-off-by: Aric Cyr <aric.cyr@amd.com>
Reviewed-by: Ashley Thomas <Ashley.Thomas2@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>