mac80211: cancel mesh path timer

commit dd4c9260e7f23f2e951cbfb2726e468c6d30306c upstream.

The mesh path timer needs to be canceled when
leaving the mesh as otherwise it could fire
after the interface has been removed already.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>