pc, i440fx: Make smm enable/disable function i440fx independent. make cpu_smm_update() generic to be independent on i440fx by registering a callback. Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp> Acked-by: Gerd Hoffmann <kraxel@redhat.com> Signed-off-by: Blue Swirl <blauwirbel@gmail.com>