adapt matrix struct to existing tests

matrix.h

@@ -8,10 +8,9 @@ typedef float MatrixType;
 // Matrixtyp
 typedef struct Matrix
 {
+    MatrixType *buffer;
     size_t rows;
     size_t cols;
-    MatrixType *buffer;
-
 } Matrix;
 
 Matrix createMatrix(unsigned int rows, unsigned int cols);