IB/mad: Rename is_data_mad to is_rmpp_data_mad

is_rmpp_data_mad is more descriptive for this function.

Reviewed-By: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Reviewed-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>