Update Unet.cpp

[kickmeplease-1]

Rows first, then columns /* @overload @param rows Number of rows in a 2D array. @param cols Number of columns in a 2D array. @param type Array type. Use CV_8UC1, ..., CV_64FC4 to create 1-4 channel matrices, or CV_8UC(n), ..., CV_64FC(n) to create multi-channel (up to CV_CN_MAX channels) matrices. / Mat(int rows, int cols, int type);

[Qengineering]

Modified also the two Raspberry Pi repos to your commit. Thanks!