Add a comment describing pmap_extract_and_hold() noting that the protection check still needs implementation on arm.
Add a comment describing pmap_extract_and_hold() noting that the protection
check still needs implementation on arm.

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