gpio/mxc: move irq_to_gpio() into gpio-mxc driver

As irq_to_gpio() is only being used by gpio-mxc driver, it should be
moved from mach/gpio.h into gpio-mxc.c.
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

arch/arm/plat-mxc/include/mach/gpio.h

@@ -34,6 +34,4 @@
 #define gpio_cansleep		__gpio_cansleep
 #define gpio_to_irq		__gpio_to_irq
 
-#define irq_to_gpio(irq)	((irq) - MXC_GPIO_IRQ_START)
-
 #endif

drivers/gpio/gpio-mxc.c

@@ -31,6 +31,8 @@
 #include <linux/of_device.h>
 #include <asm-generic/bug.h>
 
+#define irq_to_gpio(irq)	((irq) - MXC_GPIO_IRQ_START)
+
 enum mxc_gpio_hwtype {
 	IMX1_GPIO,	/* runs on i.mx1 */
 	IMX21_GPIO,	/* runs on i.mx21 and i.mx27 */