gpsd: fix nmea2000 build failure

NMEA2000 seems to require NAVCOM for some odd reason.
Fixes
http://autobuild.buildroot.net/results/91ddc286f6a92498f96aba7d312f82d5c77a689a/build-end.log


Also do a correct sort of protocol config options.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>