QNearFieldManager::registerNdefMessageHandler returns -1 on error

This brings it in line with another function overload.

Change-Id: I9120f755790e60b5073024133955c2b10671308f
Reviewed-by: Martin Leutelt <martin.leutelt@basyskom.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>