arm/imx: fix irq_base for gpio

When gpio core dynamically allocate gpio number for a port, it starts
from the end of the total range, 0 ~ ARCH_NR_GPIOS.  That said, the
earlier a port gets probed, the bigger gpio number it gets assigned.
To match this, the irq_base for gpio should be assigned from
'MXC_GPIO_IRQ_START + ARCH_NR_GPIOS' decreasingly.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
diff --git a/arch/arm/mach-imx/mach-imx6q.c b/arch/arm/mach-imx/mach-imx6q.c
index eb7531b..22aa54a 100644
--- a/arch/arm/mach-imx/mach-imx6q.c
+++ b/arch/arm/mach-imx/mach-imx6q.c
@@ -39,11 +39,10 @@
 static int __init imx6q_gpio_add_irq_domain(struct device_node *np,
 				struct device_node *interrupt_parent)
 {
-	static int gpio_irq_base = MXC_GPIO_IRQ_START + ARCH_NR_GPIOS -
-				   32 * 7; /* imx6q gets 7 gpio ports */
+	static int gpio_irq_base = MXC_GPIO_IRQ_START + ARCH_NR_GPIOS;
 
+	gpio_irq_base -= 32;
 	irq_domain_add_simple(np, gpio_irq_base);
-	gpio_irq_base += 32;
 
 	return 0;
 }