gpio: davinci: Use signed type for 'irq' variable

Variable 'irq' is declared as unsigned and then used to store
negative return values from irq_alloc_descs() such as -EINVAL.
This patch fix this by declaring the variable as a signed.
Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-davinci.c

@@ -423,7 +423,8 @@ static const struct irq_domain_ops davinci_gpio_irq_ops = {
 
 static int davinci_gpio_irq_setup(struct platform_device *pdev)
 {
-	unsigned	gpio, irq, bank;
+	unsigned	gpio, bank;
+	int		irq;
 	struct clk	*clk;
 	u32		binten = 0;
 	unsigned	ngpio, bank_irq;