Explicitely note that destroy_dev() sleeps.
Explicitely note that destroy_dev() sleeps.

Requested by:	ed (some time ago), Jaakko Heinonen <jh saunalahti fi>

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