This function had been disabled from the beginning:
see 9fddaa0c

cpu_reset() function is in target-ppc/helper.c
Signed-off-by: NThomas Monjalon <thomas@monjalon.net>
Acked-by: NAlexander Graf <agraf@suse.de>
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>