usb: core: switch bus numbering to using idr

USB bus numbering is based on directly dealing with bitmaps and
defines a separate list of busses.
This can be simplified and unified by using existing idr functionality.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index 16ade41..524c982 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -1115,6 +1115,7 @@
 	bus_unregister(&usb_bus_type);
 	usb_acpi_unregister();
 	usb_debugfs_cleanup();
+	idr_destroy(&usb_bus_idr);
 }
 
 subsys_initcall(usb_init);