libata: use the enlarged capacity after late HPA unlock

After late HPA unlock, libata kept using the original capacity
ignoring the new larger native capacity.  Enlarging device on the fly
doesn't cause any harm.  Use the larger native capacity instead.  This
will enable on-demand HPA unlocking.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>