IB/ehca: Supply QP token for SRQ base QPs

Because hardware reports the SRQ token in RWQEs of SRQ base QPs, supply the
base QP token as SRQ token, so we can properly find the SRQ base QP.

Signed-off-by: Joachim Fenkes <fenkes@de.ibm.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>