avformat/swfenc: Remove another unneeded float computation

fewer chances for rounding differences between platforms is better
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/swfenc.c

@@ -236,7 +236,7 @@ static int swf_write_header(AVFormatContext *s)
     }
 
     if (!swf->audio_enc)
-        swf->samples_per_frame = (44100.0 * rate_base) / rate;
+        swf->samples_per_frame = (44100LL * rate_base) / rate;
     else
         swf->samples_per_frame = (swf->audio_enc->sample_rate * rate_base) / rate;