IB/cm: Use correct reject code for invalid GID

Set the reject code properly when rejecting a request that contains an
invalid GID.  A suitable GID is returned by the IB CM in the
additional reject information (ARI).  This is a spec compliancy issue.

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