sata_promise: TX2plus PATA support

This patch implements a simple way of setting up per-port
flags on the SATA+PATA Promise TX2plus chips, which is a
prerequisite for supporting the PATA port on those chips.

It is based on the observation that ap->flags isn't really
used until after ->port_start() has been invoked. So it
places the "exceptional" per-port flags array in the driver's
private host structure, and uses it in ->port_start() to
finalise the port's flags.

This patch obsoletes the #promise-sata-pata branch included
in the #all branch.

Signed-off-by: Mikael Pettersson <mikpe@it.uu.se>
Signed-off-by: Jeff Garzik <jeff@garzik.org>