ARM: SAMSUNG: Add common samsung_gpiolib_to_irq function

This patch adds a common callback for gpio_to_irq() for external and
gpio interrupts for Samsung SoCs.

Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Ben Dooks <ben-linux@fluff.org>
[kgene.kim@samsung.com: moved samsung_gpiolib_to_irq() for s3c24xx build]
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
diff --git a/arch/arm/plat-samsung/gpio.c b/arch/arm/plat-samsung/gpio.c
index b83a833..7743c4b 100644
--- a/arch/arm/plat-samsung/gpio.c
+++ b/arch/arm/plat-samsung/gpio.c
@@ -157,3 +157,11 @@
 	if (ret >= 0)
 		s3c_gpiolib_track(chip);
 }
+
+int samsung_gpiolib_to_irq(struct gpio_chip *chip, unsigned int offset)
+{
+	struct s3c_gpio_chip *s3c_chip = container_of(chip,
+			struct s3c_gpio_chip, chip);
+
+	return s3c_chip->irq_base + offset;
+}