Merge branch 'mscc-RGMII'

Antoine Tenart says:

====================
net: phy: mscc: add support for RGMII MAC mode

This series adds support for the RGMII MAC mode for the VSC8584 PHY
family and for RGMII_ID modes (Tx and/or Rx).

I decided to drop the custom delay for now. I made some tests and it
seemed to be working quite well. If we find out we really need to lower
the delay, which I doubt, I'll send support for it.

Since v2:
  - Dropped support for custom dt bindings.
  - Add the 2ns delay based on the interface mode.
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Signed-off-by: David S. Miller <davem@davemloft.net>