[M] Change in coreboot[master]: soc/intel/ehl: Add EHL MDIO operation

[Mario Scheithauer (Code Review)]

Attention is currently required from: Angel Pons, Lean Sheng Tan, Werner Zeh.

Mario Scheithauer has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/69383 )

Change subject: soc/intel/ehl: Add EHL MDIO operation
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Patch Set 1:

(1 comment)

Patchset:

PS1: 
Hi Angel, it was some time ago, when I had already tried to implement a PHY driver.
https://review.coreboot.org/c/coreboot/+/64024
At that time, you had talked about a way via ops_mdio. I have now tried to implement something this way.
What do you think of this, could this be a valid way?
Thank you already for looking over.