General refactor on update on HSGMII, BASE-X ecc

[simonebortolin]

Following the introduction of PON routers with sfp w/o mac (#311), there is a need for a general refactoring to improve SFP identity and communication standards, in particolar:

• specify better the differences between PHY mmi, MAC mmi and base-X, perhaps with a diagram and with references to linux kernel management.
• creation of a table with all the various PHY mmi, MAC mmi and base-X and their eeprom values and autosentising, Signaling Rate, Encoding, Rate Identifier , ... and ref SFF-8472 Rev 12.4

https://en.wikipedia.org/wiki/Gigabit_Ethernet#Fiber_optics

https://members.snia.org/document/dl/26895

• specify in the ONT and router no longer hsgmii/base-X yes or no, but rather the standards supported by the eeprom, like ethernet on router or the new page introduced on #311
• Speed: HSGMII/2.5 Base-X is 3.125Gbps Anime4000/RTL960x#17 Anime4000/RTL960x#17 (comment)