Some Intel SoC may need preparation before reset can be properly
handled. Add callback that chip/soc code can implement.
BUG=chrome-os-partner:55055
Change-Id: I45857838e1a306dbcb9ed262b55e7db88a8944e5
Signed-off-by: Andrey Petrov <andrey.petrov@intel.com>
Reviewed-on: https://review.coreboot.org/15720
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>