hi all,
  tilapila support both dual slot and single slot. The difference should be detected by the existence of dev3. Some other RS780 mainboard has
the same function. The patch added the function to make these boards work smoothly.

Signed-off-by: Wang Qing Pei <wangqingpei@gmail.com>

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Wang Qing Pei
Phone: 86+13426369984