src/mainboard: Add vendor ELMEX with a board

Add board with amd/persimmon as template.

Change-Id: I263b54e0f49b6f1ba730c7f87de41f990ba8fe67
Signed-off-by: Yuichi Ito <yui.corebt@gmail.com>
Reviewed-on: https://review.coreboot.org/15926
Tested-by: build bot (Jenkins)
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
28 files changed