Fixed symbol clash between sensor and positioning plug-in on iOS

locationDelegate is used by two iOS plug-ins at the same time.
This removes the duplicate names and thus fixes the build if
the same application happens to use the two APIs.

Task-number: QTBUG-40198
Change-Id: I7bb0c1400f1a088a70854b522ca81ee58f1abbb0
Reviewed-by: Eike Ziller <eike.ziller@digia.com>