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>

arch/arm/mach-imx/mach-imx6q.c

@@ -39,11 +39,10 @@ static void __init imx6q_map_io(void)
 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;
 }

arch/arm/mach-mx5/imx51-dt.c

@@ -54,11 +54,10 @@ static int __init imx51_tzic_add_irq_domain(struct device_node *np,
 static int __init imx51_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 * 4; /* imx51 gets 4 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;
 }

arch/arm/mach-mx5/imx53-dt.c

@@ -58,11 +58,10 @@ static int __init imx53_tzic_add_irq_domain(struct device_node *np,
 static int __init imx53_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; /* imx53 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;
 }