Attach dwqe(4) to Intel Elkhart Lake PSE SGMII devices.

Patch by msaitoh@netbsd, who tested both PSE SGMII ports on a Helix 330.

remove unneeded includes
ok deraadt@

Add initial support for Elkhart Lake ethernet to dwqe(4).

For now, only attach to PSE0/RGMII (device ID 0x4ba0) which is the
only device I have access to for testing.

There is a known problem where

Add initial support for Elkhart Lake ethernet to dwqe(4).

For now, only attach to PSE0/RGMII (device ID 0x4ba0) which is the
only device I have access to for testing.

There is a known problem where Tx throughput is lower than expected.
This is being looked into.

ok kettenis@

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