eqos(4): Add initial support for Intel Elkhart Lake internal Ethernet devices.

- Only tested on PSE SGMII 1G Ethernet MAC with MaxLinear GPY115.
- I don't know why dmat64 doesn't work. eqos_attach() have a special
code if EQOS_HW_FEATURE_ADDR64_32BIT(sc) is true, but it seems it doesn't
work.
- TODO:
Multiqueue support.
Detach support.

branches: 1.1.2;
Add man pages for eqos(4), mcommphy(4)

lgtm jmcneill@