[POWERPC] Celleb: Move pause, kexec_cpu_down to beat.c

This is an update for "Beat on Celleb"
  - Move beat_pause(), beat_kexec_cpu_down() from setup.c to beat.c

Signed-off-by:  <Kou.Ishizaki@toshiba.co.jp>
Acked-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>