[PATCH] sata_nv: better irq handlers

nf2/3 and ck804 have irq status register.  Implement better irq
handler for those flavors of nv.  This patch makes different flavors
of nv controllers use different irq handlers by using separate
port_info for each flavor.

This change also makes following EH and hotplug updates easier to
integrate.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>