suggest to use av_get_bytes_per_sample() in av_get_bits_per_sample_format() doxy

The previously suggested replacement - av_get_bits_per_sample_fmt() -
was also deprecated.
Signed-off-by: Ronald S. Bultje <rsbultje@gmail.com>

libavcodec/avcodec.h

@@ -3847,7 +3847,7 @@ int av_get_bits_per_sample(enum CodecID codec_id);
 
 #if FF_API_OLD_SAMPLE_FMT
 /**
- * @deprecated Use av_get_bits_per_sample_fmt() instead.
+ * @deprecated Use av_get_bytes_per_sample() instead.
  */
 attribute_deprecated
 int av_get_bits_per_sample_format(enum AVSampleFormat sample_fmt);