booting with ATA-AHCI now broken

[Gary Jennejohn]

The latest commit to dev/ata/chipsets/ata-ahci.c totally breaks
booting on my machine.

I didn't save the commit message so I can't quote the exact commit
revision number.

_Every_ ata port now times out.

Here the relevant bits from pciconf:

atapci0 at pci0:0:17:0:    class=0x010601 card=0xb0021458 chip=0x43911002 rev=0x00 hdr=0x00
    vendor     = 'ATI Technologies Inc'
    class      = mass storage
    subclass   = SATA

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Gary Jennejohn