[PATCH] libata: reorganize ata_bus_probe()

Now that reset and configure are converted such that they don't modify
or disable libata core data structures, reorganize ata_bus_probe() to
reflect this change.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>