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>
diff --git a/drivers/net/declance.c b/drivers/net/declance.c
index e179aa1..00e2a8a 100644
--- a/drivers/net/declance.c
+++ b/drivers/net/declance.c
@@ -696,7 +696,7 @@
 
 static irqreturn_t lance_dma_merr_int(const int irq, void *dev_id)
 {
-	struct net_device *dev = (struct net_device *) dev_id;
+	struct net_device *dev = dev_id;
 
 	printk("%s: DMA error\n", dev->name);
 	return IRQ_HANDLED;
@@ -704,7 +704,7 @@
 
 static irqreturn_t lance_interrupt(const int irq, void *dev_id)
 {
-	struct net_device *dev = (struct net_device *) dev_id;
+	struct net_device *dev = dev_id;
 	struct lance_private *lp = netdev_priv(dev);
 	volatile struct lance_regs *ll = lp->ll;
 	int csr0;