Removed unnecessary type cast

Change-Id: I0f2d5155ec042e9b5cbe9a9d6b186b121ed7737f

vp9/encoder/vp9_onyx_if.c

@@ -2221,7 +2221,7 @@ static void calc_psnr(const YV12_BUFFER_CONFIG *a, const YV12_BUFFER_CONFIG *b,
     psnr->samples[1 + i] = samples;
     psnr->psnr[1 + i] = vp9_mse2psnr(samples, 255.0, (double) sse);
 
-    total_sse += (uint64_t)sse;
+    total_sse += sse;
     total_samples += samples;
   }