pinctrl: rockchip: emulate both edge triggered interrupts

The gpio interrupt controller on Rockchip socs can do edge triggers only
for single edges but not both. Nevertheless a lot of gpio users rely on
the availability of both-edge triggered interrupts - i.e. gpio-keys.

Therefore implement a solution similar to pinctrl-coh901 re-setting the
triggering edge depending on the gpio value in the interrupt demuxer.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>