[AE/osxsink] - allow up to 16 channels in osx sink - fixes #15261

This is a temp fix which will be fixed properly once the channel mapping PR is ready. Its ment to be easily backported to Gotham.

Well finally we found a device which had 10 channels in one stream - so the limit to 8 is faulty here (well the limit to 16 is faulty too - as said once the channelmapping PR is ready - this limit will vanish because we will be able to use the real channel map of the device/stream).

Trac ticket for reference:

http://trac.xbmc.org/ticket/15261