[Why]

Idle power states (IPS) describe levels of power-gating within DCN. DM
and DC is responsible for ensuring that we are out of IPS before any DCN
programming happens. Any DCN programming while we're in IPS leads to
undefined behavior (mostly hangs).

Because IPS intersects with all display features, the ability to disable
IPS by default while ironing out the known issues is desired. However,
disabing it completely will cause important features such as s0ix entry
to fail.

Therefore, more granular IPS debug flags are desired.

[How]

Extend the dc debug mask bits to include the available list of IPS
debug flags.

All the flags should work as documented, with the exception of
IPS_DISABLE_DYNAMIC. It requires dm changes which will be done in
later changes.

v2: enable docs and fix docstring format
Signed-off-by: Leo Li <sunpeng.li@amd.com>
Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>