libata: fix sata_link_hardreset() @online out parameter handling

The @online out parameter is supposed to set to true iff link is
online and reset succeeded as advertised in the function description
and callers are coded expecting that.  However, sata_link_reset()
didn't behave this way on device readiness test failure.  Fix it.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>