[PATCH] ata_piix: implement proper port map

Replace combined mode handling via PIIX_COMB/COMB_PATA_P0 with proper
port map.  PIIX now prints port configuration during initialization.
ATA_FLAG_SLAVE_POSS is now turned on for SATA ports only when the
slave device is actually avaliable.

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