drm/amd/display: Add new IPS config mode

[Why]
We don't have a way to specify IPS2 for display off but RCG only for
static screen and local video playback.

[How]
Add a new setting that allows RCG only when displays are active but
IPS2 when all displays are off.

Reviewed-by: Ovidiu Bunea <ovidiu.bunea@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>