schedule HR timer 200us earlier and than wait using ndelay

based on idea from
http://stackoverflow.com/questions/14944204/linux-hrtimer-microsecond-precision

Signed-off-by: Radek Dostal <radek.dostal@streamunlimited.com>
start audio instead just triggering GPIO

Signed-off-by: Radek Dostal <radek.dostal@streamunlimited.com>