Audio(osx); Fix period size calculation.
Audio(osx); Fix period size calculation.

Task-number: QTBUG-8878
Reviewed-by:Dmytro Poplavskiy

tmcguire/qt-mobility,enthought/qt-mobility,kaltsi/qt-mobility,kaltsi/qt-mobility,tmcguire/qt-mobility,enthought/qt-mobility,enthought/qt-mobility,qtproject/qt-mobility,qtproject/qt-mobility,enthought/qt-mobility,enthought/qt-mobility,kaltsi/qt-mobility,tmcguire/qt-mobility,kaltsi/qt-mobility,qtproject/qt-mobility,enthought/qt-mobility,KDE/android-qt-mobility,qtproject/qt-mobility,KDE/android-qt-mobility,KDE/android-qt-mobility,tmcguire/qt-mobility,tmcguire/qt-mobility,qtproject/qt-mobility,kaltsi/qt-mobility,KDE/android-qt-mobility,qtproject/qt-mobility,kaltsi/qt-mobility