reiserfs: fix up lockdep warnings

Add I_MUTEX_XATTR annotations to the inode locking in the reiserfs xattr code.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>