drm/amd/display: Add a Precise Delay Routine

Fix DP compliance failures 4.2.2.12, 4.3.1.21, 4.9.1.19
caused by imprecise delay on fsleep().

Reviewed-by: Aric Cyr <aric.cyr@amd.com>
Signed-off-by: Fangzhi Zuo <Jerry.Zuo@amd.com>
Signed-off-by: Wayne Lin <wayne.lin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>