usblp: poison URBs upon disconnect

[ Upstream commit 296a193b06120aa6ae7cf5c0d7b5e5b55968026e ]

syzkaller reported an URB that should have been killed to be active.
We do not understand it, but this should fix the issue if it is real.

Signed-off-by: Oliver Neukum <oneukum@suse.com>
Reported-by:  <syzbot+be5b5f86a162a6c281e6@syzkaller.appspotmail.com>
Link: https://lore.kernel.org/r/20200507085806.5793-1-oneukum@suse.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>