MFC: r287768, r290566, r290946

• Although it doesn't make a whole lot of sense to enable RX and TX before their initial configuration is done, it turns out that r281337 (MFCed to stable/9 in r285178) has the inverse effect on some older chips. Moreover, as with newer chips before, two chips seemingly identical according to their MAC revisions may behave differently in this regard, with most working but a few not, making changes extremely hard to test. Closer inspection of the corresponding Linux code suggests that RX and TX should only be enabled after their initial configuration with RTL8168G and later chips, i. e. RTL8106E{,US}, RTL8107E, as well as RTL8168{EP,G,GU,H}, so limit the new code path to these. [1]
• Distinguish between RTL8168H and RTL8107E, with the latter being the 10/100-Mbit/s-only variant of the former.
• For MAC variants that can only do Fast Ethernet at a maximum, ensure that we don't advertise Gigabit Ethernet speed.
• In re_stop(), do the inverse of re_init_locked() and enable RXDV gate on RTL8168G and later chips again, matching what Linux does.
• With the latter in place, it turns out that WOL previously only worked by accident with RTL8168G and later chips when the interface actually was brought up. This is due to the fact that with these MAC variants, RXDV gate needs be disabled for WOL to work. So in re_setwol() do just that when IFCAP_WOL is requested.
• Add preliminary support for RTL8168H and RTL8107E, with the latter being the 10/100-Mbit/s-only variant of the former.