gpio: Use irq_desc_get_xxx() to avoid redundant lookup of irq_desc

Use irq_desc_get_xxx() to avoid redundant lookup of irq_desc while we
already have a pointer to corresponding irq_desc.

Preparatory patch for the removal of the 'irq' argument from irq flow
handlers.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Alexandre Courbot <gnurou@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

drivers/gpio/gpio-omap.c

@@ -714,7 +714,7 @@ static void omap_gpio_irq_handler(unsigned int irq, struct irq_desc *desc)
 	struct gpio_bank *bank;
 	int unmasked = 0;
 	struct irq_chip *irqchip = irq_desc_get_chip(desc);
-	struct gpio_chip *chip = irq_get_handler_data(irq);
+	struct gpio_chip *chip = irq_desc_get_handler_data(desc);
 
 	chained_irq_enter(irqchip, desc);