Merge branch 'xgmac_mdio-preamble-suppression-and-custom-MDC-frequerncies'

Tobias Waldekranz says:

====================
net/fsl: xgmac_mdio: Preamble suppression and custom MDC frequencies

The first patch removes the docs for a binding that has never been
supported by the driver as far as I can see. This is a bit of a
mystery to me, maybe Freescale/NXP had/has support for it in an
internal version?

We then start working on the xgmac_mdio driver, converting the driver
to exclusively use managed resources, thereby simplifying the error
paths. Suggested by Andrew.

Preamble suppression is then added, followed by MDC frequency
customization. Neither code will change any bits if the corresponding
dt properties are not specified, so as to not trample on any setup
done by the bootloader, which boards might have relied on up to now.

Finally, we document the new bindings.

Tested on a T1023 based board.
====================

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