vchiq: Take care of a corner case tickled by VCSM

Closing a connection that isn't fully open requires care, since one
side does not know the other side's port number. Code was present to
handle the case where a CLOSE is sent immediately after an OPEN, i.e.
before the OPENACK has been received, but this was incorrectly being
used when an OPEN from a client using port 0 was rejected.

(In the observed failure, the host was attempting to use the VCSM
service, which isn't present in the 'cutdown' firmware. The failure
was intermittent because sometimes the keepalive service would
grab port 0.)

This case can be distinguished because the client's remoteport will
still be VCHIQ_PORT_FREE, and the srvstate will be OPENING. Either
condition is sufficient to differentiate it from the special case
described above.