ARM: shmobile: kzm9g: use gpio-keys instead of gpio-keys-polled

6e20a0a4
(gpio: pcf857x: enable gpio_to_irq() support) supports
gpio_to_irq() on pcf857x driver.
Now, we can use gpio-keys driver instead of gpio-keys-polled.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms@verge.net.au>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>