BB10: do not mix up pixel width and height

This fixes the aspect ratio calculation for video windows.

Change-Id: Ie4762b98ee805a41031e1ba88f5cd353426dfdf8
Reviewed-by: Bernd Weimer <bweimer@blackberry.com>
Reviewed-by: Tobias Koenig <tobias.koenig.qnx@kdab.com>
Reviewed-by: Thomas McGuire <thomas.mcguire@kdab.com>