afs: proc cells and rootcell are writeable

Both proc files are writeable and used for configuring cells. But
there is missing correct mode flag for writeable files. Without
this patch both proc files are read only.

[ It turns out they aren't really read-only, since root can write to
  them even if the write bit isn't set due to CAP_DAC_OVERRIDE ]
Signed-off-by: NPali Rohár <pali.rohar@gmail.com>
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/afs/proc.c

@@ -130,8 +130,8 @@ int afs_proc_init(void)
 	if (!proc_afs)
 		goto error_dir;
 
-	if (!proc_create("cells", 0, proc_afs, &afs_proc_cells_fops) ||
-	    !proc_create("rootcell", 0, proc_afs, &afs_proc_rootcell_fops))
+	if (!proc_create("cells", 0644, proc_afs, &afs_proc_cells_fops) ||
+	    !proc_create("rootcell", 0644, proc_afs, &afs_proc_rootcell_fops))
 		goto error_tree;
 
 	_leave(" = 0");