drm/amd/display: Added delay to DPM log

HW registers were being read to quickly, causing incorrect values to be
logged after a clock frequency was changed

Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Martin Leung <martin.leung@amd.com>
Acked-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: Relja Vojvodic <relja.vojvodic@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>