consitify do_mount() arguments

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/include/linux/fs.h b/include/linux/fs.h
index ec911ae..9baf827 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2075,7 +2075,7 @@
 extern void kern_unmount(struct vfsmount *mnt);
 extern int may_umount_tree(struct vfsmount *);
 extern int may_umount(struct vfsmount *);
-extern long do_mount(char *, char *, char *, unsigned long, void *);
+extern long do_mount(const char *, const char *, const char *, unsigned long, void *);
 extern struct vfsmount *collect_mounts(struct path *);
 extern void drop_collected_mounts(struct vfsmount *);
 extern int iterate_mounts(int (*)(struct vfsmount *, void *), void *,