drm/amdgpu: fix cleaning up reserved VMID on release

We need to reset this or otherwise run into list corruption later on.

Fixes: e44a0fe6 ("drm/amdgpu: rework reserved VMID handling")
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Tested-by: Candice Li <candice.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c

@@ -497,6 +497,7 @@ void amdgpu_vmid_free_reserved(struct amdgpu_device *adev,
 	    !--id_mgr->reserved_use_count) {
 		/* give the reserved ID back to normal round robin */
 		list_add(&id_mgr->reserved->list, &id_mgr->ids_lru);
+		id_mgr->reserved = NULL;
 	}
 	vm->reserved_vmid[vmhub] = false;
 	mutex_unlock(&id_mgr->lock);