[netdrvr] irq handler minor cleanups in several drivers

* use irq_handler_t where appropriate

* no need to use 'irq' function arg, its already stored in a data struct

* rename irq handler 'irq' argument to 'dummy', where the function
  has been analyzed and proven not to use its first argument.

* remove always-false "dev_id == NULL" test from irq handlers

* remove pointless casts from void*

* declance: irq argument is not const

* add KERN_xxx printk prefix

* fix minor whitespace weirdness

Signed-off-by: Jeff Garzik <jgarzik@redhat.com>