IB/srpt: Move the code for parsing struct ib_cm_req_event_param

This patch does not change any functionality but makes srpt_cm_req_recv()
independent of the IB/CM and hence simplifies the patch that introduces
RDMA/CM support.

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>