drm/amdgpu/gfx12: return early in preempt_ib()

When MES is enabled KIQ is not available.  Return an error
when someone uses the debugfs preempt test interface in
that case.
Acked-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/gfx_v12_0.c

@@ -4501,6 +4501,9 @@ static int gfx_v12_0_ring_preempt_ib(struct amdgpu_ring *ring)
 	struct amdgpu_ring *kiq_ring = &kiq->ring;
 	unsigned long flags;
 
+	if (adev->enable_mes)
+		return -EINVAL;
+
 	if (!kiq->pmf || !kiq->pmf->kiq_unmap_queues)
 		return -EINVAL;