drm/amdgpu: free hw_vm_fence when fail in amdgpu_job_alloc

If drm_sched_job_init fails, hw_vm_fence is not freed currently,
then cause memory leak.

Fixes: db36632ea51e ("drm/amdgpu: clean up and unify hw fence handling")
Link: https://lore.kernel.org/amd-gfx/[e-mail]/T/#t
Signed-off-by: Jiqian Chen <[e-mail]>
Reviewed-by: Amos Kong <[e-mail]>
Reviewed-by: Alex Deucher <[e-mail]>
Reviewed-by: Christian König <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>
(cherry picked from commit 5d42ee457ccd1fb5da4c7f817825b2806ec36956)

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

···
 	if (!entity)
 		return 0;
 
-	return drm_sched_job_init(&(*job)->base, entity, 1, owner,
-				  drm_client_id);
+	r = drm_sched_job_init(&(*job)->base, entity, 1, owner, drm_client_id);
+	if (!r)
+		return 0;
+
+	kfree((*job)->hw_vm_fence);
 
 err_fence:
 	kfree((*job)->hw_fence);