Clarify that bus_dma does not stall future load requests once a load is deferred.  The caller is required to enforce that if that is desired.
Clarify that bus_dma does not stall future load requests once a load is
deferred.  The caller is required to enforce that if that is desired.

MFC after:	2 weeks

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase