pata_of_platform: Don't use NO_IRQ

Drivers should not use NO_IRQ; moreover, some architectures don't
have it nowadays. '0' is the 'no irq' case.

Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>