[GFS2] Mark file_operations const

As per Arjan's patches:
http://www.kernel.org/git/?p=linux/kernel/git/steve/gfs2-2.6.git;a=commitdiff;h=99ac48f54a91d02140c497edc31dc57d4bc5c85d
and
http://www.kernel.org/git/?p=linux/kernel/git/steve/gfs2-2.6.git;a=commitdiff;h=4b6f5d20b04dcbc3d888555522b90ba6d36c4106

make the GFS2 file_operations structures const.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/gfs2/ops_file.h b/fs/gfs2/ops_file.h
index a2edce3..46302b5 100644
--- a/fs/gfs2/ops_file.h
+++ b/fs/gfs2/ops_file.h
@@ -14,7 +14,7 @@
 			      struct file_ra_state *ra_state,
 			      char *buf, loff_t *pos, unsigned size);
 
-extern struct file_operations gfs2_file_fops;
-extern struct file_operations gfs2_dir_fops;
+extern const struct file_operations gfs2_file_fops;
+extern const struct file_operations gfs2_dir_fops;
 
 #endif /* __OPS_FILE_DOT_H__ */