merged poweroff fix from dlech's repo
Merge branch 'master' of https://github.com/mindboards/ev3dev-kernel
added sound driver to config
set sample rate to 22050 Hz
reduced volume range to 0..100 and improved accuracy of duty_ticks calculation
introduce defines for easy configuration of audio and PWM
introduced tasklet to reduce PWM irq runtime
introduced sysfs attributes for tone and volume; applied volume to tone
Merge branch 'sound_experiments'

* sample rate is now 22050 (still heavy crackling)
* alsa driver improvements
* added sysfs attributes for mode, tone and volume
* applied volume setting to tone