jpeg2000dec: silence unused variable warning

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/jpeg2000dec.c

@@ -1557,7 +1557,7 @@ static int jp2_find_codestream(Jpeg2000DecoderContext *s)
                     atom2_size -= 2;
                     for (; n>0; n--) {
                         int cn   = bytestream2_get_be16(&s->g);
-                        int typ  = bytestream2_get_be16(&s->g);
+                        int av_unused typ  = bytestream2_get_be16(&s->g);
                         int asoc = bytestream2_get_be16(&s->g);
                         if (cn < 4 || asoc < 4)
                             s->cdef[cn] = asoc;