net: hns3: Fix for rx priv buf allocation when DCB is not supported

When hdev doesn't support DCB, rx private buffer is not allocated,
otherwise there is not enough buffer for rx shared buffer, causing
buffer allocation process to fail.
This patch fixes by checking the dcb capability in
hclge_rx_buffer_calc.

Fixes: 46a3df9f ("net: hns3: Add HNS3 Acceleration Engine & Compatibility Layer Support")
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>