fix gpu HOG implementation:
fix gpu HOG implementation:

move hog::set_up_constants from constructor to compute method

if user changed CUDA device between constructor and computation,
some variables were uninitialized
(cherry picked from commit 21bbed7bafd25114ff15d8012f3f8619d258d0c1)

opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv