iw_cxgb4: stop MPA_REPLY timer when disconnecting

There exists a race where the application can setup a connection
and then disconnect it before iw_cxgb4 processes the fw4_ack
message.  For passive side connections, the fw4_ack message is
used to know when to stop the ep timer for MPA_REPLY messages.

If the application disconnects before the fw4_ack is handled then
c4iw_ep_disconnect() needs to clean up the timer state and stop the
timer before restarting it for the disconnect timer.  Failure to do this
results in a "timer already started" message and a premature stopping
of the disconnect timer.

Fixes: e4b76a2a ("RDMA/iw_cxgb4: stop_ep_timer() after MPA negotiation")

Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>