exynos5420: flush caches and disable MMU in resume path

This patch flushes the caches and disables the MMU before resuming.

c32b9b3 ("Set up caching in the bootblock.") had a bug where the
dcache and MMU remained enabled in the resume path. This caused
the machine to hang on resume. However, other bugs were preventing
us from testing this properly earlier on so it went unnoticed until
now.

Signed-off-by: David Hendricks <dhendrix@chromium.org>
BUG=none
BRANCH=none
TEST=Built and booted on pit, powerd_dbus_suspend works again,
"suspend_stress_test --memory_check" ran 10 times without problems.

Change-Id: Ib1774f09d286a4d659da9fc2dad1d7a6fc1ebe5e
Reviewed-on: https://chromium-review.googlesource.com/67007
Reviewed-by: ron minnich <rminnich@chromium.org>
Commit-Queue: David Hendricks <dhendrix@chromium.org>
Tested-by: David Hendricks <dhendrix@chromium.org>

src/cpu/samsung/exynos5420/wakeup.c

@@ -17,6 +17,7 @@
  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#include <arch/cache.h>
 #include <console/console.h>
 #include "power.h"
 #include "wakeup.h"
@@ -27,6 +28,8 @@ void wakeup(void)
 		power_reset();
 
 	power_init();  /* Ensure ps_hold_setup() for early wakeup. */
+	dcache_mmu_disable();
+	icache_invalidate_all();
 	power_exit_wakeup();
 	/* Should never return. */
 	die("Failed to wake up.\n");