Fix trivial typos in anon_inodes.c comments

Trivial typo and grammar fixes.

Signed-off-by: "J. Bruce Fields" <bfields@citi.umich.edu>
Cc: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>