sim: dv-sockser: push module init prototype down

sim: dv-sockser: push module init prototype down

Pull out the duplicated dv_sockser_install prototype from the tconfig.in
files and put it in the one place it gets used -- sim-module.c.  This is
still arguably incorrect, but it's better than the status quo where the
tconfig.in has to include header files and duplicate the dv-sockser func.
The tconfig header is meant to be simple and contain a target defines.