remove_proc_subtree() doesn't work here as local->ddev has already
been removed, and NULLed out.  Use proc_remove() instead.
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>
Tested-by: NRussell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>