ffmpeg: Fix bistream typos

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

ffmpeg.c

@@ -2648,7 +2648,7 @@ static int init_output_bsfs(OutputStream *ost)
 
         ret = av_bsf_init(ctx);
         if (ret < 0) {
-            av_log(NULL, AV_LOG_ERROR, "Error initializing bistream filter: %s\n",
+            av_log(NULL, AV_LOG_ERROR, "Error initializing bitstream filter: %s\n",
                    ost->bsf_ctx[i]->filter->name);
             return ret;
         }

ffmpeg_opt.c

@@ -1345,7 +1345,7 @@ static OutputStream *new_output_stream(OptionsContext *o, AVFormatContext *oc, e
 
         ret = av_bsf_alloc(filter, &ost->bsf_ctx[ost->nb_bitstream_filters]);
         if (ret < 0) {
-            av_log(NULL, AV_LOG_ERROR, "Error allocating a bistream filter context\n");
+            av_log(NULL, AV_LOG_ERROR, "Error allocating a bitstream filter context\n");
             exit_program(1);
         }