avcodec/j2kenc: Fix funky bpno errors on decoding

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 816676085e)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/j2kenc.c

@@ -658,11 +658,10 @@ static void encode_cblk(Jpeg2000EncoderContext *s, Jpeg2000T1Context *t1, Jpeg20
 
     if (max == 0){
         cblk->nonzerobits = 0;
-        bpno = 0;
     } else{
         cblk->nonzerobits = av_log2(max) + 1 - NMSEDEC_FRACBITS;
-        bpno = cblk->nonzerobits - 1;
     }
+    bpno = cblk->nonzerobits - 1;
 
     cblk->data[0] = 0;
     ff_mqc_initenc(&t1->mqc, cblk->data + 1);