Hibernation: Move function prototypes to header

This patch moves the prototypes of count_highmem_pages() and
restore_highmem() to kernel/power/power.h

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Len Brown <len.brown@intel.com>