CoreAudio: fix supported input and output channel count.

Only the maximum number of channels was reported as being supported.
We now report all possible configurations up to the maximum number of
channels to be supported.

Task-number: QTBUG-34639
Change-Id: Ib4c599ea8b772ebeaaca95137d24bac49dbd80d3
Reviewed-by: Christian Stromme <christian.stromme@digia.com>
Reviewed-by: Ivan Romanov <drizt@land.ru>
Reviewed-by: Andy Nichols <andy.nichols@digia.com>