gpio: rcar: Support both edge trigger with DT

Some versions of the R-Car GPIO controller support triggering on both
edges of the input signal. Whether this capability is supported is
currently specified in platform data. R-Car GPIO devices instantiated
from the device tree have the capability turned off even when the
hardware supports it.

To fix this, add DT match data support to the driver, initialize both
edge trigger support from match data and enable both edge trigger in
r8a7790 and r8a7791 match data.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>