[PATCH] libata: propogate host private data from probe function

This will let me chop the code size of several drivers right down. In
many cases the actual private data is very useful and constant for a
given host controller so being able to just pass it at probe time would
be very useful indeed (eg with the via driver would could pass the udma
clocking and reduce the code size, or with the AMD one the UDMA
multiplier and the offset)

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>