drivers: irda: fix sign bug

platform_get_irq_byname() can return negative results, it is not seen to
unsigned irq. Make it signed.
Signed-off-by: Kulikov Vasiliy <segooon@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/irda/sh_sir.c

@@ -709,7 +709,7 @@ static int __devinit sh_sir_probe(struct platform_device *pdev)
 	struct sh_sir_self *self;
 	struct resource *res;
 	char clk_name[8];
-	unsigned int irq;
+	int irq;
 	int err = -ENOMEM;
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);