ehea: Fix a copy-paste err in ehea_init_port_res

pr->tx_bytes should be assigned to tx_bytes other than
rx_bytes.

Reported-by: Hulk Robot <hulkci@huawei.com>
Fixes: ce45b873 ("ehea: Fixing statistics")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Signed-off-by: David S. Miller <davem@davemloft.net>