h264: remove useless assignment.

source index, as well as dest one, is unconditionnaly set afterwards,
before being effectively used.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/h264.c

@@ -296,7 +296,6 @@ const uint8_t *ff_h264_decode_nal(H264Context *h, const uint8_t *src,
     // use second escape buffer for inter data
     bufidx = h->nal_unit_type == NAL_DPC ? 1 : 0;
 
-    si = h->rbsp_buffer_size[bufidx];
     av_fast_padded_malloc(&h->rbsp_buffer[bufidx], &h->rbsp_buffer_size[bufidx], length+MAX_MBPAIR_SIZE);
     dst = h->rbsp_buffer[bufidx];