Fix integer overflow in estimateMoovBoxSize

On 200GB SD Card the Camera reported an expected max file duration
of 89158000000 us, this later overflowed the calculation in
estimateMoovBoxSize. Move the division in before the multiplication
to avoid the overflow (this gives different result for <1ms duration
limits but this should not be noticeable in the end).

Change-Id: I53e8238745ef86282483b617df5dcbd3562907fc