IB/mad: Add support for additional MAD info to/from drivers

In order to support alternate sized MADs (and variable sized MADs on OPA
devices) add in/out MAD size parameters to the process_mad core call.

In addition, add an out_mad_pkey_index to communicate the pkey index the driver
wishes the MAD stack to use when sending OPA MAD responses.

The out MAD size and the out MAD PKey index are required by the MAD
stack to generate responses on OPA devices.

Furthermore, the in and out MAD parameters are made generic by specifying them
as ib_mad_hdr rather than ib_mad.

Drivers are modified as needed and are protected by BUG_ON flags if the MAD
sizes passed to them is incorrect.

Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>