Clobber registers as appropriate in AMD CAR code, and

Clobber registers as appropriate in AMD CAR code, and
build a better barrier for gcc to reflush all registers
when moving the stack.  memcpy was taken from Linux.

Signed-off-by: Rudolf Marek <r.marek@assembler.cz>
Acked-by: Patrick Georgi <patrick.georgi@coresystems.de>
git-svn-id: svn://svn.coreboot.org/coreboot/trunk@5153 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1