ao_null accepts float input, but the code calculating ao_data.bps only
checked for 1-byte formats and used samplesize 2 for everything else.
Because ao_null uses the bps value in its timing calculations this
effectively made "playback" advance at half the correct speed.
Fixed by calculating samplesize with af_fmt2bits() instead.
git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@25223 b3059339-0415-0410-9bf9-f77b7e298cf2