Ethernet driver

[neuschaefer]

The Nuvoton Ethernet MAC Controller (EMC) is shared between the older, deleted W90P910 platform, WPCM450, and NPCM7xx. Currently, there is no EMC driver in mainline. There are two ways forward:

• Upstream the npcm7xx-emc driver in openbmc/dev-5.10
• Revive the w90p910 driver ← I'm doing this

Depends on the reset driver (#8).

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• [ ] test how large a frame the hardware can actually handle
• [ ] finish refactoring
  • [x] devm_*
  • [x] better queue index names
  • [ ] answer all TODOs
• [x] ethtool support for speed and duplex mode
• [x] NAPI (maybe)
• [ ] investigate/fix: Why do the packets stop flowing after too many link mode changes?
• [ ] send upstream
• [ ] get it merged
• [ ] DMA (maybe)