A hack basically.. We have a bunch of code that used to call

A hack basically..  We have a bunch of code that used to call
devsw_module_handler() indirectly and not use the chain arguments.  To
eliminate this indirection via that function (which does nothing now)
without duplicating a modevent handler into all the routines that don't
presently have one, supply a NOP (do nothing, return OK) routine which
is functionally equivalent to what's there now.  This is a hack and is
still wrong, because there doesn't appear to be anything to reclaim
resources on an unload of a module with one of these in it.  I'm not
sure whether to make the NOP handler refuse a MOD_UNLOAD event or what.