Request and free the GPIO line used for the beeper properly.
Then use the gpiolib API to flip the output of the GPIO pin
instead of relying on hacks to poke the register bits.

Cc: Imre Kaloz <kaloz@openwrt.org>
Cc: Alexandre Courbot <acourbot@nvidia.com>
Acked-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>
Acked-by: NArnd Bergmann <arnd@arndb.de>
Acked-by: NKrzysztof Halasa <khc@pm.waw.pl>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>