libata: legacy mode fixes , take #2

For a legacy ATA controller, libata registers two separate host sets problems. There are two patch use the same way to fix this problems, but the SIMPLEX flag is still assigned to both host_sets of legacy primary/secondary port.

http://marc.theaimsgroup.com/?l=linux-ide&m=115012115213127&w=2
http://marc.theaimsgroup.com/?l=linux-ide&m=114475219522457&w=2

This patch try to fix the problems by

1. Let both legacy ports share the same host_set for the ATA_HOST_SIMPLEX to work.
2. Add per port irq to ata_ioports for legacy irq 14/15 since host_set is shared now.
3. Add legacy irq handler (ata_nonshared_interrupt) to support legacy mode irq.
4. Pass struct ata_port* to request_irq() on legacy mode.

(Patch against the upstream branch)

Unicorn Chang