[arm] fix 3x3s2p0 avg pooling crash (#3754)

* fix pooling overflow, test=develop

* fix conflict test=develop

lite/backends/arm/math/pooling.cc

@@ -2701,7 +2701,9 @@ void pooling3x3s2p0_avg(const float* din,
     w_unroll_size -= 1;
     w_unroll_remian = wout - w_unroll_size * 4;
   }
-
+  //  do overflow process
+  w_unroll_size -= 1;
+  w_unroll_remian += 4;
   auto zero_ptr =
       static_cast<float*>(TargetMalloc(TARGET(kARM), win * sizeof(float)));
   memset(zero_ptr, 0, win * sizeof(float));