drm/amd/display: Revert "DP link layer test 4.2.1.1 fix due to specs update"

[why]
The change causes some regression in a common use case.
Will need more investigation before fixing the original issue.

[how]
This reverts commit fb8cf277.

Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>