ACPI: bus: Introduce acpi_bus_for_each_dev()

In order to avoid exposing acpi_bus_type to modules, introduce an
acpi_bus_for_each_dev() helper for iterating over all ACPI device
objects and make typec_link_ports() use it instead of the raw
bus_for_each_dev() along with acpi_bus_type.

Having done that, drop the acpi_bus_type export.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>