Compile cbmem.c instead of including it in romstage,

Compile cbmem.c instead of including it in romstage,
and do that only if resume is done.

Signed-off-by: Rudolf Marek <r.marek@assembler.cz>
Acked-by: Patrick Georgi <patrick@georgi-clan.de>
git-svn-id: svn://svn.coreboot.org/coreboot/trunk@6174 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1