drm/amdkfd: Fix getting unique_id in topology

Since the unique_id is now obtained in amdgpu in smu_late_init,
topology misses getting the value during KFD device initialization.
To work around this, we use amdgpu_amdkfd_get_unique_id to get
the unique_id at read time. Due to this, we can remove unique_id from
the kfd_dev structure, since we only need it in the KFD node properties
struct

Signed-off-by: Kent Russell <kent.russell@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>