[PATCH] powerpc: make powerbook_sleep_grackle static

powerbook_sleep_grackle is only called inside via-pmu, from pmu_ioctl()

Signed-off-by: Olaf Hering <olh@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>