ACPI: add acpi_bus_get_status_handle()

Add acpi_bus_get_status_handle() so we can get the status of a namespace
object before building a struct acpi_device.

This removes a use of "device->flags.dynamic_status", a cached indicator of
whether _STA exists.  It seems simpler and more reliable to just evaluate
_STA and catch AE_NOT_FOUND errors.

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

include/acpi/acpi_bus.h

@@ -322,6 +322,8 @@ extern void unregister_acpi_bus_notifier(struct notifier_block *nb);
 
 int acpi_bus_get_device(acpi_handle handle, struct acpi_device **device);
 void acpi_bus_data_handler(acpi_handle handle, void *context);
+acpi_status acpi_bus_get_status_handle(acpi_handle handle,
+				       unsigned long long *sta);
 int acpi_bus_get_status(struct acpi_device *device);
 int acpi_bus_get_power(acpi_handle handle, int *state);
 int acpi_bus_set_power(acpi_handle handle, int state);