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/irda/donauboe.c b/drivers/net/irda/donauboe.c
index 7a91281..636d063 100644
--- a/drivers/net/irda/donauboe.c
+++ b/drivers/net/irda/donauboe.c
@@ -657,12 +657,6 @@
   return xbofs;
 }
 
-static int toshoboe_invalid_dev(int irq)
-{
-  printk (KERN_WARNING DRIVER_NAME ": irq %d for unknown device.\n", irq);
-  return 1;
-}
-
 #ifdef USE_PROBE
 /***********************************************************************/
 /* Probe code */
@@ -711,12 +705,9 @@
 static irqreturn_t
 toshoboe_probeinterrupt (int irq, void *dev_id)
 {
-  struct toshoboe_cb *self = (struct toshoboe_cb *) dev_id;
+  struct toshoboe_cb *self = dev_id;
   __u8 irqstat;
 
-  if (self == NULL && toshoboe_invalid_dev(irq))
-    return IRQ_NONE;
-
   irqstat = INB (OBOE_ISR);
 
 /* was it us */