e1000e: cleanup strict checkpatch MEMORY_BARRIER checks

Add comments to memory barriers per strict checkpatch.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
1 file changed