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/sunqe.c

@@ -468,7 +468,7 @@ static void qe_tx_reclaim(struct sunqe *qep);
  */
 static irqreturn_t qec_interrupt(int irq, void *dev_id)
 {
-	struct sunqec *qecp = (struct sunqec *) dev_id;
+	struct sunqec *qecp = dev_id;
 	u32 qec_status;
 	int channel = 0;