chromeos: add get_recovery_mode_from_vbnv() to vbnv_flash

The first platform that used flash-backed VBNV data has a physical
recovery switch, get_recovery_mode_from_vbnv() was never implemented.

This patch adds get_recovery_mode_from_vbnv() similarly to how it's
implemented for other vbnv storage in other places.

BUG=chrome-os-partner:34436
BRANCH=none
TEST=needs testing

Change-Id: Ifd795c5c1ff0f23619fd2125b4795571af03ece1
Signed-off-by: Stefan Reinauer <reinauer@chromium.org>
Original-Commit-Id: 09f1bf96089bf9d159e4220c1f4d99388d709545
Original-Signed-off-by: David Hendricks <dhendrix@chromium.org>
Original-Change-Id: I9cf18c988eaa4b7e720d6c66a02b1c5c63b473e9
Original-Reviewed-on: https://chromium-review.googlesource.com/239978
Original-Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: http://review.coreboot.org/9563
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/vendorcode/google/chromeos/vbnv_flash.c

@@ -15,6 +15,8 @@
  * 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
+ *
+ * TODO: Make this CAR-friendly in case we use it on x86 some day.
  */
 
 #include <cbfs.h>
@@ -25,6 +27,7 @@
 #include <vb2_api.h>
 #include <vboot_nvstorage.h>
 #include "chromeos.h"
+#include "vbnv_layout.h"
 
 #if IS_ENABLED(CONFIG_VBOOT_VERIFY_FIRMWARE)
 #define BLOB_SIZE VBNV_BLOCK_SIZE
@@ -189,3 +192,10 @@ void save_vbnv(const uint8_t *vbnv_copy)
 		printk(BIOS_ERR, "failed to save nvdata\n");
 	}
 }
+
+int get_recovery_mode_from_vbnv(void)
+{
+	if (!is_initialized())
+		init_vbnv();
+	return cache[RECOVERY_OFFSET];
+}