[binutils-gdb] sim: dv-sockser: add stub funcs when not available

[sergiodj+buildbot@redhat.com]

*** TEST RESULTS FOR COMMIT 3649cb065699316bc8cd64b06f273c72f1806323 ***

Author: Mike Frysinger <vapier@gentoo.org>
Branch: master
Commit: 3649cb065699316bc8cd64b06f273c72f1806323

sim: dv-sockser: add stub funcs when not available
This lets ports assume that the dv-sockser API is always available if
they want to.  This way we don't have to do an abort at configure time
and it makes the resulting code a bit simpler.