Add write line routine which is called indirectly by FSP. TEST=Build and run on Galileo Gen2. Change-Id: Idefb6e9ebe5a2b614055dabddc1882bfa3bba673 Signed-off-by: Lee Leahy <leroy.p.leahy@intel.com> Reviewed-on: https://review.coreboot.org/16127 Tested-by: build bot (Jenkins) Reviewed-by: Martin Roth <martinroth@google.com>