cpu/intel: Add configuration for socket LGA1155

This allows mainboards to explicitly select LGA1155.

Change-Id: Id33679b27c89038588347cb4f1a6a0e66aae3e6e
Signed-off-by: Damien Zammit <damien@zamaudio.com>
Reviewed-on: http://review.coreboot.org/7197
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Tested-by: build bot (Jenkins)