ata_pci_init_one() is the only function which uses ops->irq_handler
and pi->sht. Other initialization functions take the same information
as arguments. This causes confusion and duplicate unused entries in
structures.
Make ata_pci_init_one() take sht as an argument and use ata_interrupt
implicitly. All current users use ata_interrupt and if different irq
handler is necessary open coding ata_pci_init_one() using
ata_prepare_sff_host() and ata_activate_sff_host can be done under ten
lines including error handling and driver which requires custom
interrupt handler is likely to require custom initialization anyway.
As ata_pci_init_one() was the last user of ops->irq_handler, this
patch also kills the field.