Refine accuracy_op.cu

[chengduoZH]

It seems that these code are unnecessary.

Paddle/paddle/operators/accuracy_op.cu

Lines 91 to 100 in 0f1c685

	int d_num_samples, d_num_correct;
	float d_accuracy;
	platform::GpuMemcpyAsync(&d_num_correct, correct_data, sizeof(int),
	cudaMemcpyDeviceToHost, stream);
	platform::GpuMemcpyAsync(&d_num_samples, total_data, sizeof(int),
	cudaMemcpyDeviceToHost, stream);
	platform::GpuMemcpyAsync(&d_accuracy, accuracy_data, sizeof(float),
	cudaMemcpyDeviceToHost, stream);
	}
	};