#include "ns_types.h" when it is not needed

[LiyouZhou]

https://github.com/ARMmbed/mbed-trace/blob/master/mbed-trace/mbed_trace.h#L55

[jupe]

@tommikas: there shouldn't be ns_types.h include when ipv6 feature is disabled or any other libservice dependencies either, but seems that this is not covered right now :(

[ciarmcom]

ARM Internal Ref: IOTSYST-1205

[tommikas]

@jupe, is this still relevant?

[jupe]

I think this is still relevant. At least there is YOTTA specific flags.. should add also mbed-os-5 flags...