drm/amd/display: Add optional optimization for IPS handshake

drm/amd/display: Add optional optimization for IPS handshake

[Why]
It's possible to skip parts of the eval and exit sequencing if we know
whether DCN is in IPS2 already or if it's committed to going to idle
and not in IPS2.

[How]
Skip IPS2 entry/exit if DMCUB is idle but the IPS2 commit is not set.

Skip the eval delay if DMCUB is already in IPS2 since we know we need
to exit.

These are turned off by default.

Reviewed-by: Duncan Ma <duncan.ma@amd.com>
Acked-by: Wayne Lin <wayne.lin@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>