pinctrl: intel: Initialize GPIO properly when used through irqchip

When a GPIO is requested using gpiod_get_* APIs the intel pinctrl driver
switches the pin to GPIO mode and makes sure interrupts are routed to
the GPIO hardware instead of IOAPIC. However, if the GPIO is used
directly through irqchip, as is the case with many I2C-HID devices where
I2C core automatically configures interrupt for the device, the pin is
not initialized as GPIO. Instead we rely that the BIOS configures the
pin accordingly which seems not to be the case at least in Asus X540NA
SKU3 with Focaltech touchpad.

When the pin is not properly configured it might result weird behaviour
like interrupts suddenly stop firing completely and the touchpad stops
responding to user input.

Fix this by properly initializing the pin to GPIO mode also when it is
used directly through irqchip.

Fixes: 7981c001 ("pinctrl: intel: Add Intel Sunrisepoint pin controller and GPIO support")
Reported-by: Daniel Drake <drake@endlessm.com>
Reported-and-tested-by: Chris Chiu <chiu@endlessm.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>