[PATCH] libata: re-initialize parameters before configuring

In ata_dev_configure(), reinitialize parameters before configuring.
This change is for revalidation and hotplug.  As ata_dev_configure()
can be entered multiple times, parameters need to be reinitialized.

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