[2.6.17 backport] VIA VT8251 SATA support

I added the PCI ID for the VT8251 IDE controller and since then I've 
been getting a continuous flow of emails from people who think I might 
have some clue about the SATA side. I don't even own the hardware, but I 
have backported the patch for inclusion in the Gentoo kernels now that 
it has been merged into the 2.6.18 tree. This patch is reported to work 
with 2.6.17.

NOTE: This is unsupported by me, and unsupported the Linux IDE/SATA 
developers too. The patch is slightly ugly because it includes a 
backport of the ata_wait_register() function so the end product is that 
we have some code using ata_wait_register() and some using whatever the 
predecessor was.

Hoping for fewer emails about this annoying hardware...
;)
Daniel