gpio-rcar: Use OUTDT when reading GPIOs configured as output

Testing on r8a7790 shows that INDT does not indicate the correct
pin state when reading a GPIO configured as output, so update
the gpio_rcar_get() function to handle this case.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>