Fix the sorting kernels used in the CenterNet pre and post-processing.

This commit moves the kernels in the correct sub-directory.
It creates new header file for Thrust kernels. It splits the
kernels into two files: 'normalize.cu' contains CenterNet
pre-processing operations, 'postprocessing.cu' contains the
CenterNet post-processing operations.

Signed-off-by: Davide Sapienza <sapienza.dav@gmail.com>

src/kernels/normalize.cu

@@ -0,0 +1,16 @@
+#include "kernelsThrust.h"
+
+__global__
+void normalize_kernel(float *bgr, const int dim, const float *mean, const float *stddev){
+    int i = blockDim.x*blockIdx.x + threadIdx.x;
+    int j = blockIdx.y;
+    bgr[j*(dim)+i] = bgr[j*(dim)+i] - mean[j];
+    bgr[j*(dim)+i] = bgr[j*(dim)+i] / stddev[j];
+    
+}
+
+void normalize(float *bgr, const int ch, const int h, const int w, const float *mean, const float *stddev){
+    int num_thread = 256;
+    dim3 dimBlock(h*w/num_thread, ch);
+    normalize_kernel<<<dimBlock, num_thread, 0>>>(bgr, h*w, mean, stddev);
+}