Improve bufdone_finish()'s handling of the bogus page.  Specifically, if one or more mappings to the bogus page must be replaced, call pmap_qenter() just once.  Previously, pmap_qenter() was called for each mapping to the bogus page.
Improve bufdone_finish()'s handling of the bogus page.  Specifically, if
one or more mappings to the bogus page must be replaced, call pmap_qenter()
just once.  Previously, pmap_qenter() was called for each mapping to the
bogus page.

MFC after:	3 weeks

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