pata-rb532-cf: remove set_irq_type from finish_io

The driver has been tested without the call to set_irq_type at this
point and occurs to work fine, so it should be safe to remove it.

Signed-off-by: Phil Sutter <n0-1@freewrt.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>