ACPI / scan: Clear match_driver flag in acpi_bus_trim()

Drivers should not bind to struct acpi_device objects that
acpi_bus_trim() has been called for, so make that function
clear flags.match_driver for those objects.

If that is not done, an ACPI driver may theoretically try to operate
a device that is not physically present.

Fixes: 202317a5

 (ACPI / scan: Add acpi_device objects for all device nodes in the namespace)
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Toshi Kani <toshi.kani@hp.com>