ACPI: acpi_bus_unregister_driver() returns void

Nobody looks at the return value, and this brings it into line with
pci_unregister_driver(), etc.  Also removed validation of the driver
pointer passed in to register and unregister.  More consistent, and we'll
find bugs faster if we fault rather than returning an error that's ignored.

Also makes internal functions acpi_device_unregister() and
acpi_driver_detach() void, since nobody uses their returns either.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index 6dca3d5..809eb50 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -327,7 +327,7 @@
 int acpi_bus_generate_event(struct acpi_device *device, u8 type, int data);
 int acpi_bus_receive_event(struct acpi_bus_event *event);
 int acpi_bus_register_driver(struct acpi_driver *driver);
-int acpi_bus_unregister_driver(struct acpi_driver *driver);
+void acpi_bus_unregister_driver(struct acpi_driver *driver);
 int acpi_bus_add(struct acpi_device **child, struct acpi_device *parent,
 		 acpi_handle handle, int type);
 int acpi_bus_trim(struct acpi_device *start, int rmdevice);