Add fs/eventfd.c to filesystems docbook.
Make typo corrections in fs/eventfd.c.
Signed-off-by: NRandy Dunlap <randy.dunlap@oracle.com>
Cc: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>