 Fix compilationw warning, by casting type to difference_type
 Fix compilationw warning, by casting type to difference_type

 bug 1822985

Jobs: 1822985-2006
[git-p4: depot-paths = "//sw/gpgpu/thrust/": change = 21248290]

andrewcorrigan/thrust-multi-permutation-iterator,jaredhoberock/thrust,jaredhoberock/thrust,andrewcorrigan/thrust-multi-permutation-iterator,thrust/thrust,thrust/thrust,thrust/thrust,jaredhoberock/thrust,thrust/thrust,jaredhoberock/thrust,andrewcorrigan/thrust-multi-permutation-iterator,thrust/thrust,jaredhoberock/thrust