drm/amdgpu: fix ip count query for xcp partitions

fix wrong ip count INFO on spatial partitions. update the query
to return the instance count corresponding to the partition id.

v2:
 initialize variables only when required to be (Christian)
 move variable declarations to the beginning of function (Christian)

Signed-off-by: Sathishkumar S <sathishkumar.sundararaju@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>