PDC 20276 RAID support in 2.4.18

Arjan and others,

I have added support for the PDC 20276 used on Gigabyte GA-8IHXP (and 
possibly other motherboards) to the ATARAID feature of the linux 2.4.18 
kernel.  I have tested that the pdcraid.c code works with this device.

I suspect you can drive this patch into the mainline kernel, but if you 
know of a better person, please advise.

Thanks!
-steve