drm/amd/display: Add entry and exit counters

[WHY & HOW]
Add new counters in the shared IPS firmware state.

Acked-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Anthony Koo <anthony.koo@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>