udp-server: Update a comment in config.h.tmpl
udp-server: Update a comment in config.h.tmpl

Expand on the SERVER_IP* entries.

Signed-off-by: Andrew Clayton <02e0a999c50b1f88df7a8f5a04e1b76b35ea6a88@zeta.digital-domain.net>

ac000/udp-fwder