sh: provide generic arch_debugfs_dir.

While sh previously had its own debugfs root, there now exists a
common arch_debugfs_dir prototype, so we switch everything over to
that.  Presumably once more architectures start making use of this
we'll be able to just kill off the stub kdebugfs wrapper.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

arch/sh/mm/pmb.c

@@ -866,11 +866,9 @@ static int __init pmb_debugfs_init(void)
 	struct dentry *dentry;
 
 	dentry = debugfs_create_file("pmb", S_IFREG | S_IRUGO,
-				     sh_debugfs_root, NULL, &pmb_debugfs_fops);
+				     arch_debugfs_dir, NULL, &pmb_debugfs_fops);
 	if (!dentry)
 		return -ENOMEM;
-	if (IS_ERR(dentry))
-		return PTR_ERR(dentry);
 
 	return 0;
 }