dt-bindings: net: convert enetc to yaml

Convert enetc device binding file to yaml. Split to 3 yaml files,
'fsl,enetc.yaml', 'fsl,enetc-mdio.yaml', 'fsl,enetc-ierb.yaml'.

Additional Changes:
- Add pci<vendor id>,<production id> in compatible string.
- Ref to common ethernet-controller.yaml and mdio.yaml.
- Add Wei fang, Vladimir and Claudiu as maintainer.
- Update ENETC description.
- Remove fixed-link part.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20240709214841.570154-1-Frank.Li@nxp.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>