drm/amd/display: Re-enable IPS2 for static screen

[Why]
IPS stability was fixed in bios.

[How]
Set disable_ips init flag to DMUB_IPS_ENABLE.

Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Acked-by: Wayne Lin <wayne.lin@amd.com>
Signed-off-by: Roman Li <roman.li@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>