change pool to pool2d

test=develop

paddle/fluid/lite/kernels/arm/pool_compute_test.cc

@@ -272,4 +272,4 @@ TEST(pool, retrive_op) {
 }  // namespace lite
 }  // namespace paddle
 
-USE_LITE_KERNEL(pool, kARM, kFloat, kNCHW, def);
+USE_LITE_KERNEL(pool2d, kARM, kFloat, kNCHW, def);

paddle/fluid/lite/operators/pool_op_test.cc

@@ -86,5 +86,5 @@ TEST(pool_op_lite, test) {
 }  // namespace paddle
 
 #ifdef LITE_WITH_ARM
-USE_LITE_KERNEL(pool, kARM, kFloat, kNCHW, def);
+USE_LITE_KERNEL(pool2d, kARM, kFloat, kNCHW, def);
 #endif