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/wan/cycx_main.c b/drivers/net/wan/cycx_main.c
index 12363e0..6e5f1c8 100644
--- a/drivers/net/wan/cycx_main.c
+++ b/drivers/net/wan/cycx_main.c
@@ -303,9 +303,9 @@
  */
 static irqreturn_t cycx_isr(int irq, void *dev_id)
 {
-	struct cycx_device *card = (struct cycx_device *)dev_id;
+	struct cycx_device *card = dev_id;
 
-	if (!card || card->wandev.state == WAN_UNCONFIGURED)
+	if (card->wandev.state == WAN_UNCONFIGURED)
 		goto out;
 
 	if (card->in_isr) {