Make camera metadata tag definitions more robust to mismatches.

Use array assignment-by-index syntax to make sure we match the desired
index to the entry, so it's easier to keep the metadata header and the
info structures in sync.

Change-Id: I06d1ea3d52c651b447cc167cd551e907c8e001ab
diff --git a/camera/src/camera_metadata.c b/camera/src/camera_metadata.c
index c7121ca..1991835 100644
--- a/camera/src/camera_metadata.c
+++ b/camera/src/camera_metadata.c
@@ -13,10 +13,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-
+#define _GNU_SOURCE // for fdprintf
 #include <system/camera_metadata.h>
 #include <cutils/log.h>
-#define _GNU_SOURCE // for fdprintf
 #include <stdio.h>
 #include <stdlib.h>
 #include <errno.h>