gpio / ACPI: register to ACPI events automatically

Instead of asking each driver to register to ACPI events we can just call
acpi_gpiochip_register_interrupts() for each chip that has an ACPI handle.
The function checks chip->to_irq and if it is set to NULL (a GPIO driver
that doesn't do interrupts) the function does nothing.

We also add the a new header drivers/gpio/gpiolib.h that is used for
functions internal to gpiolib and add ACPI GPIO chip registering functions
to that header.

Once that is done we can remove call to acpi_gpiochip_register_interrupts()
from its only user, pinctrl-baytrail.c

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpiolib.h

@@ -0,0 +1,23 @@
+/*
+ * Internal GPIO functions.
+ *
+ * Copyright (C) 2013, Intel Corporation
+ * Author: Mika Westerberg <mika.westerberg@linux.intel.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef GPIOLIB_H
+#define GPIOLIB_H
+
+#ifdef CONFIG_ACPI
+void acpi_gpiochip_add(struct gpio_chip *chip);
+void acpi_gpiochip_remove(struct gpio_chip *chip);
+#else
+static inline void acpi_gpiochip_add(struct gpio_chip *chip) { }
+static inline void acpi_gpiochip_remove(struct gpio_chip *chip) { }
+#endif
+
+#endif /* GPIOLIB_H */