ACPI: factor out device type and status checking

This patch adds acpi_bus_type_and_status(), which determines the type
of the object and whether we want to build an acpi_device for it.  If
it is acpi_device-worthy, it returns the type and the device's current
status.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Len Brown <len.brown@intel.com>