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/sunqe.c b/drivers/net/sunqe.c
index 020e781..7874eb1 100644
--- a/drivers/net/sunqe.c
+++ b/drivers/net/sunqe.c
@@ -468,7 +468,7 @@
  */
 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;