libata: Integrate ACPI-based PATA/SATA hotplug - version 5

Modern laptops with hotswap bays still tend to utilise a PATA interface
on a SATA bridge, generally with the host controller in some legacy
emulation mode rather than AHCI. This means that the existing hotplug
code in libata is unable to work. The ACPI specification states that
these devices can send notifications when hotswapped, which avoids the
need to obtain notification from the controller. This patch uses the
existing libata-acpi code and simply registers a notification in order
to trigger a rescan whenever the firmware signals an event.

Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>