lavc/dolby_e_parser: #include avcodec.h explicitly

This file uses definitions from it, but relies on an indirect include
through get_bits.h

libavcodec/dolby_e_parser.c

@@ -18,6 +18,7 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#include "avcodec.h"
 #include "dolby_e.h"
 #include "get_bits.h"
 #include "put_bits.h"