RDMA/cma: Add ability to specify type of service

Provide support to specify a type of service for a communication
identifier.  A new function call is used when dealing with IPv4
addresses.  For IPv6 addresses, the ToS is specified through the
traffic class field in the sockaddr_in6 structure.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>
[ The comments Eitan Zahavi and myself have made over the v1 post at
  <http://lists.openfabrics.org/pipermail/general/2007-August/039247.html>
  were fully addressed. ]

Reviewed-by: Or Gerlitz <ogerlitz@voltaire.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>