drm/amdgpu: fix potential resource leak warning

Clear resource leak warning that when the prepare fails,
the allocated amdgpu job object will never be released.
Signed-off-by: Tim Huang <Tim.Huang@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -102,6 +102,11 @@ static int amdgpu_vm_sdma_prepare(struct amdgpu_vm_update_params *p,
 	if (!r)
 		r = amdgpu_sync_push_to_job(&sync, p->job);
 	amdgpu_sync_free(&sync);
+
+	if (r) {
+		p->num_dw_left = 0;
+		amdgpu_job_free(p->job);
+	}
 	return r;
 }