IB/cm: Update XRC support based on XRC annex errata

The XRC annex was updated to have XRC behave more like RD. Specifically,
the XRC TGT QPN moves from the local QPN to local EECN field.  Lookup of
SRQN is done using the REQ/REP protocol.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>