IB/mthca: Fix MAD extended header format for MAD_IFC firmware command

Several fields in an incoming MAD extended info header were passed
into the MAD_IFC firmware command at incorrect offsets (mostly off by
4 bytes).  As the result, the HCA will fail to generate traps in which
this info is needed (e.g. traps which include the GRH of the incoming
packet), in violation of the IB spec.

Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>