drm/amdgpu: fix ring timeout issue in gfx10 sr-iov environment

commit 26c95e838e63 ("drm/amdgpu: set the VM pointer to NULL in
amdgpu_job_prepare") set job->vm as NULL if there is no fence. It will
cause emit switch buffer be skippen if job->vm set as NULL.

Check job rather than vm could solve this problem.

Fixes: 26c95e838e63 ("drm/amdgpu: set the VM pointer to NULL in amdgpu_job_prepare")
Signed-off-by: Lin.Cao <[e-mail]>
Reviewed-by: Alex Deucher <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

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

···
 	amdgpu_ring_patch_cond_exec(ring, cond_exec);
 
 	ring->current_ctx = fence_ctx;
-	if (vm && ring->funcs->emit_switch_buffer)
+	if (job && ring->funcs->emit_switch_buffer)
 		amdgpu_ring_emit_switch_buffer(ring);
 
 	if (ring->funcs->emit_wave_limit &&