Tilapila supports both dual slot and single slot. The difference should be

Tilapila supports 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>
Acked-by: Zheng Bao <zheng.bao@amd.com>
git-svn-id: svn://svn.coreboot.org/coreboot/trunk@5714 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1