arch/power8: Rename to ppc64

POWER8 is a specific implementation of ppc64, which is by now outdated
(POWER9 has been on the market for a while). Rename arch/power8/ to
potentially cover a wider range of hardware.

TEST=Toolchains built before/after this commit can build coreboot for
     emulation/qemu-power8 from before/after this commit.

Change-Id: I2d6f08b12a9ffc8a652ddcd6f24ad85ecb33ca52
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-on: https://review.coreboot.org/c/29943
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Timothy Pearson <tpearson@raptorengineering.com>

src/arch/ppc64/boot.c

@@ -0,0 +1,23 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2013 Google Inc.
+ *
+ * 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; version 2 of the License.
+ *
+ * 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.
+ */
+
+#include <program_loading.h>
+
+void arch_prog_run(struct prog *prog)
+{
+	void (*doit)(void *) = prog_entry(prog);
+
+	doit(prog_entry_arg(prog));
+}