gpsd: nmea2000 requires aivdm support

Fixes:
http://autobuild.buildroot.org/results/853cac5becf9d071c6ec1181e1e951bc8e7d80d5/build-end.log


and tons of identical build failures.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>