avcodec/videotoolbox: Fix bistream typo

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

libavcodec/videotoolbox.c

@@ -81,7 +81,7 @@ CFDataRef ff_videotoolbox_avcc_extradata_create(AVCodecContext *avctx)
 {
     CFDataRef data = NULL;
 
-    /* Each VCL NAL in the bistream sent to the decoder
+    /* Each VCL NAL in the bitstream sent to the decoder
      * is preceded by a 4 bytes length header.
      * Change the avcC atom header if needed, to signal headers of 4 bytes. */
     if (avctx->extradata_size >= 4 && (avctx->extradata[4] & 0x03) != 0x03) {