Beep is a target-independent software that can handle buzzers controlled by kmod-gpio-beeper.
This change is useful for some non-x86 enterprise APs and development boards
that have a buzzer connected to GPIO.
Compile-tested: ath79, ELECOM WAB-I1750-PS, 3fab4ac + device support patch
Run-tested: ath79, ELECOM WAB-I1750-PS, 3fab4ac + device support patch
Signed-off-by: Yanase Yuki <dev@zpc.sakura.ne.jp>