dwifslpreproc: Fix strides of images input to applytopup
dwifslpreproc: Fix strides of images input to applytopup

For non-RAS images, the absence of this option resulted in inappropriate correction of EPI distortions, which in turn led to derivation of a sub-optimal mask for eddy.

MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3