exportfs: make struct export_operations const

Now that nfsd has stopped writing to the find_exported_dentry member we an
mark the export_operations const

Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Neil Brown <neilb@suse.de>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: <linux-ext4@vger.kernel.org>
Cc: Dave Kleikamp <shaggy@austin.ibm.com>
Cc: Anton Altaparmakov <aia21@cantab.net>
Cc: David Chinner <dgc@sgi.com>
Cc: Timothy Shimmin <tes@sgi.com>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Chris Mason <mason@suse.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: "Vladimir V. Saveliev" <vs@namesys.com>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Mark Fasheh <mark.fasheh@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/isofs/isofs.h

@@ -178,4 +178,4 @@ isofs_normalize_block_and_offset(struct iso_directory_record* de,
 extern const struct inode_operations isofs_dir_inode_operations;
 extern const struct file_operations isofs_dir_operations;
 extern const struct address_space_operations isofs_symlink_aops;
-extern struct export_operations isofs_export_ops;
+extern const struct export_operations isofs_export_ops;