drm/amd/display: Revert dram_clock_change_latency for DCN2.1

[WHY & HOW]
Using values provided by DF for latency may cause hangs in
multi display configurations. Revert change to previous value.

Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Sung Lee <sung.lee@amd.com>
Reviewed-by: Haonan Wang <Haonan.Wang2@amd.com>
Acked-by: Eryk Brol <eryk.brol@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>