ACPI: add newline in power.c message

Add newline to printk so that the message is on a line
by itself and not merged with something unrelated to it.

Reported-by: Toralf Förster <toralf.foerster@gmx.de>
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>