Don't use default Timer for audio output write_timed #32
Description
The current implementation of audio.py specifies the freq argument for the pyb.DAC.write_timed method (used to play sounds) as an integer rather than providing an instantiated timer, causing it to use the default timer 6. This means that if a user tries to use a pyb.DAC in their task and specifies a write_timed freq argument as an integer, this will try and use the same timer and will not work when both outputs are used at the same time.
The implementation of the pyControl audio module shoud not use integer freq arguments to write timed and should instead instantiate a time explicitly to avoid this problem.