extcon: max14577: fix handling return value of regmap_irq_get_virq

The function can return negative values, so its result should
be assigned to signed variable.

The problem has been detected using proposed semantic patch
scripts/coccinelle/tests/assign_signed_to_unsigned.cocci [1].

[1]: http://permalink.gmane.org/gmane.linux.kernel/2046107

Signed-off-by: Andrzej Hajda <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Chanwoo Choi <[e-mail]>

drivers/extcon/extcon-max14577.c

···
 	/* Support irq domain for max14577 MUIC device */
 	for (i = 0; i < info->muic_irqs_num; i++) {
 		struct max14577_muic_irq *muic_irq = &info->muic_irqs[i];
-		unsigned int virq = 0;
+		int virq = 0;
 
 		virq = regmap_irq_get_virq(max14577->irq_data, muic_irq->irq);
 		if (virq <= 0)