netlink: Add a way to "hot unplug" SVC

Currently, there is no way to remove the SVC.
So, if SVC is removed and added again, it won't be reinitialized.
To remove SVC, we have to remove the hd driver.
Add a new netlink operation to remove and register again the hd driver.

Signed-off-by: Alexandre Bailon <abailon@baylibre.com>