gpio/rockchip: fix get_direction value handling

The function uses the newly introduced rockchip_gpio_readl_bit()
which directly returns the actual value of the requeste bit.
So using the existing bit-wise check for the bit inside the value
will always return 0.

Fix this by dropping the bit manipulation on the result.

Fixes: 3bcbd1a8

 ("gpio/rockchip: support next version gpio controller")
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>