proresenc_kostya: fix encoded mantissa.

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

libavcodec/proresenc_kostya.c

@@ -289,8 +289,7 @@ static inline void encode_vlc_codeword(PutBitContext *pb, unsigned codebook, int
         exponent = av_log2(val);
 
         put_bits(pb, exponent - exp_order + switch_bits, 0);
-        put_bits(pb, 1, 1);
-        put_bits(pb, exponent, val);
+        put_bits(pb, exponent + 1, val);
     } else {
         exponent = val >> rice_order;