tegra124: Call into the mainboard bootblock init if one exists.

We should seperate out the mainboard specific parts of the bootblock so that
they can be customized as necessary.

BUG=None
TEST=Built and booted into the bootblock on nyan.
BRANCH=None

Change-Id: Ia633a68521725f6e88341608ccdbedc4f1ce8223
Signed-off-by: Gabe Black <gabeblack@google.com>
Reviewed-on: https://chromium-review.googlesource.com/172581
Reviewed-by: Ronald Minnich <rminnich@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Tested-by: Gabe Black <gabeblack@chromium.org>
Commit-Queue: Gabe Black <gabeblack@chromium.org>

src/soc/nvidia/tegra124/bootblock.c

@@ -18,6 +18,7 @@
  */
 
 #include <arch/hlt.h>
+#include <bootblock_common.h>
 #include <cbfs.h>
 #include <console/console.h>
 
@@ -42,6 +43,8 @@ void main(void)
 	if (CONFIG_BOOTBLOCK_CONSOLE)
 		console_init();
 
+	bootblock_mainboard_init();
+
 	entry = cbfs_load_stage(CBFS_DEFAULT_MEDIA, "fallback/romstage");
 
 	hlt();