SFP+ support for 8168fp/8117

[Kai Heng Feng <kai.heng.feng@canonical.com>]

Hi Heiner,

There's an 8168fp/8117 chip has SFP+ port instead of RJ45, the phy device ID matches "Generic FE-GE Realtek PHY" nevertheless.
The problems is that, since it uses SFP+, both BMCR and BMSR read are always zero, so Realtek phylib never knows if the link is up.

However, the old method to read through MMIO correctly shows the link is up:
static unsigned int rtl8169_xmii_link_ok(struct rtl8169_private *tp)
{
       return RTL_R8(tp, PHYstatus) & LinkStatus;
}

Few ideas here:
- Add a link state callback for phylib like phylink's phylink_fixed_state_cb(). However there's no guarantee that other parts of this chip works.
- Add SFP+ support for this chip. However the phy device matches to "Generic FE-GE Realtek PHY" which may complicate things.

Any advice will be welcome.

Kai-Heng