Merge branch 'dwmac-mediatek-add-more-support-for-RMII'

Biao Huang says:

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net-next: stmmac: dwmac-mediatek: add more support for RMII

changes in v2:
 PATCH 1/2 net-next: stmmac: mediatek: add more support for RMII
        As Andrew's comments, add the "rmii_internal" clock to the list of clocks.

 PATCH 2/2 net-next: dt-binding: dwmac-mediatek: add more description for RMII
        document the "rmii_internal" clock in dt-bindings
        rewrite the sample dts in dt-bindings.

v1:
This series is for support RMII when MT2712 SoC provides the reference clock.
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Signed-off-by: David S. Miller <davem@davemloft.net>