We want to ensure that the tx work has finished before returning from
the ldisc close op, so do a synchronous cancel.
Reported-by: NJiri Slaby <jirislaby@kernel.org>
Signed-off-by: NJeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: NJakub Kicinski <kuba@kernel.org>