driver core: add BUS_NOTIFY_UNBOUND_DRIVER event

This patch adds a new bus notifier event which is emitted _after_ a
device is removed from its driver. This event will be used by the
dma-api debug code to check if a driver has released all dma allocations
for that device.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 742cbe6..efd00de 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -320,6 +320,10 @@
 		devres_release_all(dev);
 		dev->driver = NULL;
 		klist_remove(&dev->p->knode_driver);
+		if (dev->bus)
+			blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
+						     BUS_NOTIFY_UNBOUND_DRIVER,
+						     dev);
 	}
 }