ACPI / glue: Drop .find_bridge() callback from struct acpi_bus_type

After PCI and USB have stopped using the .find_bridge() callback in
struct acpi_bus_type, the only remaining user of it is SATA, but SATA
only pretends to be a user, because it points that callback to a stub
always returning -ENODEV.

For this reason, drop the SATA's dummy .find_bridge() callback and
remove .find_bridge(), which is not used any more, from struct
acpi_bus_type entirely.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Yinghai Lu <yinghai@kernel.org>
Acked-by: Jeff Garzik <jgarzik@pobox.com>