drm/amdgpu: Add xcp manager num_xcp_per_mem_partition

Used by KFD to check memory limit accounting.

Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>