connector: convert to single-threaded workqueue

From: Evgeniy Polyakov <johnpol@2ka.mipt.ru>

We don't need one cqueue thread for each CPU.  cqueue is used for
receiving userspace datagrams, which are very rare and thus will
happily live with a single queue.

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>