QLowEnergyController/CentralManager - cleanup (OS X/iOS)

Get rid of all 'hand-written' function/method signatures in qCWarnings
and Q_ASSERTS, use Q_FUNC_INFO instead. Fix error function for
characteristic/descriptor write errors - remove unused parameter.

Change-Id: I4f3f7c6c6a06802135f47a4b5cbb7c4313af4f34
Reviewed-by: Alex Blasche <alexander.blasche@theqtcompany.com>