SB600 has four write once LPC ROM protect areas. It is not possible to write

SB600 has four write once LPC ROM protect areas. It is not possible to write
enable that area once the register is set so print a warning.

Signed-off-by: Marc Jones <marcj.jones@amd.com>
Acked-by: Ronald G. Minnich <rminnich@gmail.com>
Acked-by: Peter Stuge <peter@stuge.se>
Acked-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
git-svn-id: svn://svn.coreboot.org/coreboot/trunk@3659 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1