drm/amd/display: Add total_num_dpps_required field to informative structure

[Why]
The informative structure needs to be extended by the total number of DPPs
required per each active plane.
The new informative field is going to be used as a statistical indicator.

[How]
The dml2_core_calcs_get_informative() routine must count a total number of DPPs.

Reviewed-by: Austin Zheng <austin.zheng@amd.com>
Signed-off-by: Oleh Kuzhylnyi <okuzhyln@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>