Kill off hotplug.h and just make net devices normal reference-counted

structures.

DHCP still broken and #if 0'd out.

src/core/hotplug.c

@@ -1,45 +0,0 @@
-/*
- * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License as
- * published by the Free Software Foundation; either version 2 of the
- * License, or any later version.
- *
- * This program is distributed in the hope that it will be useful, but
- * WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
- */
-
-#include <assert.h>
-#include <gpxe/hotplug.h>
-
-/** @file
- *
- * Hotplug support
- *
- */
-
-/**
- * Forget all persistent references to an object
- *
- * @v list		List of persistent references
- */
-void forget_references ( struct list_head *list ) {
-	struct reference *ref;
-	struct reference *ref_tmp;
-
-	list_for_each_entry_safe ( ref, ref_tmp, list, list ) {
-		ref->forget ( ref );
-	}
-
-	/* The list had really better be empty by now, otherwise we're
-	 * screwed.
-	 */
-	assert ( list_empty ( list ) );
-}