Rename uboot/halt.c to dummy/halt.c.

It's not U-Boot specific and it's a stub.

grub-core/lib/dummy/halt.c

@@ -0,0 +1,32 @@
+/*
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2013  Free Software Foundation, Inc.
+ *
+ *  GRUB 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 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  GRUB 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 GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <grub/misc.h>
+#include <grub/mm.h>
+#include <grub/kernel.h>
+#include <grub/loader.h>
+
+void
+grub_halt (void)
+{
+  grub_machine_fini (GRUB_LOADER_FLAG_NORETURN);
+
+  /* Just stop here */
+
+  while (1);
+}