r8169: add support for RTL8168 series add-on card.

[ Upstream commit 610c9087 ]

This chip is the same as RTL8168, but its device id is 0x8161.

Signed-off-by: Chun-Hao Lin <hau@realtek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>