ata(4) support for IXP600 and IXP700

[Andrey V. Elsukov]

Xin LI wrote:
> I did not found a clue how the restriction would be useful, so if
> someone with real hardware or has specs can provide me some more
> information it will help me to make sure.

Resources savings :))
I can't found specs, but linux atiixp driver don't allocate resources
for the second channel and it's probably written by ATI.
Anyway it's not critical (i guess).

-- 
WBR, Andrey V. Elsukov