[PATCH] libata: convert dev->id to pointer

Convert dev->id from array to pointer.  This is to accomodate
revalidation.  During revalidation, both old and new IDENTIFY pages
should be accessible and single ->id array doesn't cut it.

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