- JMC260 with full mask revision 2 and ECO revision 0 does not support

- JMC260 with full mask revision 2 and ECO revision 0 does not support
  64bits DMA operatoin.
- Newer parts (full mask revision >= 2) of JMC250/JMC260 require driver
  to configure TX offload engine and TX MAC clock source according to the
  current link speed.
- New datasheet no longer uses PCI revision ID to identify chip generation,
  but chipmode's full mask revision and ECO revision are used; update
  driver accordingly.

Thank Ethan <ethanhsiao@jmicron.com> for pointing out necessary updates
and sending me an EVB.