gpio: arizona: Correct check whether the pin is an input

The logic to check if the pin is an input or output whilst testing if we
need to read the register value from the hardware or not is currently
inverted. Remove the erroneous not from the if statement.

Fixes: 11598d17

 ("gpio: arizona: Correct handling for reading input GPIOs")
Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>