ACPI / gpio: Add support for naming GPIOs

Now that we have the new helper function that sets nice names for GPIO
lines based on "gpio-line-names" device property, we can take advantage of
this in acpi_gpiochip_add().

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>