drm/amdgpu: fix memory leak in amdgpu_vm_update_page_directory

If amdgpu_ib_get() fails we returned the error code but we missed
freeing ib.

Cc: "Christian König" <christian.koenig@amd.com>
Cc: Jammy Zhou <Jammy.Zhou@amd.com>
Cc: Chunming Zhou <david1.zhou@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "monk.liu" <monk.liu@amd.com>
Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

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

@@ -455,8 +455,10 @@ int amdgpu_vm_update_page_directory(struct amdgpu_device *adev,
 		return -ENOMEM;
 
 	r = amdgpu_ib_get(ring, NULL, ndw * 4, ib);
-	if (r)
+	if (r) {
+		kfree(ib);
 		return r;
+	}
 	ib->length_dw = 0;
 
 	/* walk over the address space and update the page directory */