ARM: sunxi_defconfig: Enable INPUT_EVDEV so axp20x-pek can be used

sunxi_defconfig already enables INPUT_AXP20X_PEK, but the device is not
exposed to userspace. Enable INPUT_EVDEV so it is.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>