lib/atomic64_test: fix missing include of linux/kernel.h

Fix a build-failure
(http://kisskb.ellerman.id.au/kisskb/buildresult/2601239/

) by adding the
missing include file (linux/kernel.h) for printk and KERN_INFO.

Signed-off-by: Peter Huewe <peterhuewe@gmx.de>
LKML-Reference: <201005241913.o4OJDKdf010884@imap1.linux-foundation.org>
Cc: Luca Barbieri <luca@luca-barbieri.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>