pinctrl: qcom: add get_direction function

The get_direction callback function allows gpiolib to know the current
direction (input vs output) for a given GPIO.

This is particularly useful on ACPI systems, where the GPIOs are
configured only by firmware (typically UEFI), so the only way to
know the initial values to query the hardware directly.  Without
this function, gpiolib thinks that all GPIOs are configured for
input.

Signed-off-by: Timur Tabi <timur@codeaurora.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>