gpio: twl4030: Cache the direction and output states in private data

Use more coherent locking in the driver. Use bitfield to store the GPIO
direction and if the pin is configured as output store the status also in a
bitfiled.
In this way we can just look at these bitfields when we need information
about the pin status and only reach out to the chip when it is needed.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>