net: make ndev->irq signed for error handling

There is a bug in cpsw_probe() where we do:

	ndev->irq = platform_get_irq(pdev, 0);
	if (ndev->irq < 0) {

The problem is that "ndev->irq" is unsigned so the error handling
doesn't work.  I have changed it to a regular int.
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -1132,7 +1132,7 @@ struct net_device {
 	unsigned long		mem_end;	/* shared mem end	*/
 	unsigned long		mem_start;	/* shared mem start	*/
 	unsigned long		base_addr;	/* device I/O address	*/
-	unsigned int		irq;		/* device IRQ number	*/
+	int			irq;		/* device IRQ number	*/
 
 	/*
 	 *	Some hardware also needs these fields, but they are not