Add UCB RISCV support for architecture, soc, and emulation mainboard..

Works in the RISCV version of QEMU.

Note that the lzmadecode is so unclean that it needs a lot of work.
A cleanup is in progress.

We decided in Prague to do this as one thing, because it forms a nice case study
of the bare minimum you need to add to get a new architecture going in qemu.

Change-Id: If5af15c3a70733d219973e0d032746f8ab027e4d
Signed-off-by: Ronald G. Minnich <rminnich@gmail.com>
Reviewed-on: http://review.coreboot.org/7584
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: build bot (Jenkins)

src/arch/riscv/bootblock_simple.c

@@ -0,0 +1,73 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2014 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.
+ *
+ * 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., 51 Franklin St, Fifth Floor, Boston,
+ * MA 02110-1301 USA
+ */
+
+#include <bootblock_common.h>
+#include <arch/cache.h>
+#include <arch/hlt.h>
+#include <arch/stages.h>
+#include <arch/exception.h>
+#include <cbfs.h>
+#include <console/console.h>
+
+static int boot_cpu(void)
+{
+	/*
+	 * FIXME: This is a stub for now. All non-boot CPUs should be
+	 * waiting for an interrupt. We could move the chunk of assembly
+	 * which puts them to sleep in here...
+	 */
+	return 1;
+}
+
+void main(void)
+{
+	const char *stage_name = CONFIG_CBFS_PREFIX"/romstage";
+	void *entry = NULL;
+
+	/* Globally disable MMU, caches, and branch prediction (these should
+	 * be disabled by default on reset) */
+	dcache_mmu_disable();
+
+	/*
+	 * Re-enable icache and branch prediction. MMU and dcache will be
+	 * set up later.
+	 *
+	 * Note: If booting from USB, we need to disable branch prediction
+	 * before copying from USB into RAM (FIXME: why?)
+	 */
+
+	if (boot_cpu()) {
+		//bootblock_cpu_init();
+		//bootblock_mainboard_init();
+	}
+
+#ifdef CONFIG_BOOTBLOCK_CONSOLE
+	console_init();
+	exception_init();
+#endif
+
+	entry = cbfs_load_stage(CBFS_DEFAULT_MEDIA, stage_name);
+
+	printk(BIOS_SPEW, "stage_name %s, entry %p\n", stage_name, entry);
+
+	if (entry) stage_exit(entry);
+	hlt();
+}