Merge branch 'gmii2rgmii-loopback'

Gerhard Engleder says:

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Add Xilinx GMII2RGMII loopback support

The Xilinx GMII2RGMII driver overrides PHY driver functions in order to
configure the device according to the link speed of the PHY attached to
it. This is implemented for a normal link but not for loopback.

Andrew told me to use phy_loopback and this changes make phy_loopback
work in combination with Xilinx GMII2RGMII.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>