drivers/net: eliminate irq handler impossible checks, needless casts

- Eliminate check for irq handler 'dev_id==NULL' where the
  condition never occurs.

- Eliminate needless casts to/from void*

Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/net/eexpress.c

@@ -796,13 +796,6 @@ static irqreturn_t eexp_irq(int irq, void *dev_info)
 	unsigned short ioaddr,status,ack_cmd;
 	unsigned short old_read_ptr, old_write_ptr;
 
-	if (dev==NULL)
-	{
-		printk(KERN_WARNING "eexpress: irq %d for unknown device\n",
-		       irq);
-		return IRQ_NONE;
-	}
-
 	lp = netdev_priv(dev);
 	ioaddr = dev->base_addr;