ntp: fix comment typos

Bernhard Schiffner noticed I had a few comment typos in this patch,
(note: to save embarrassment, when making typos, avoid copying and
pasting them) so this patch corrects them.

[ Impact: cleanup ]

Reported-by: Bernhard Schiffner <bernhard@schiffner-limbach.de>
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Cc: riel@redhat.com
Cc: akpm@linux-foundation.org
LKML-Reference: <1242090794.7214.131.camel@localhost.localdomain>
Signed-off-by: Ingo Molnar <mingo@elte.hu>