input: misc: ixp4-beeper: switch to use gpiolib

The platform using this beeper has support for gpiolib, so there
is no point to use the custom gpio_line* API. A strange ambiguity
where a line was first set as input and then driven high was
solved by first driving the line high as output and then switch
it to input.

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