Add PHY register descriptions for some of useful phys

This is first cleaned PR to extend ethernet functions to other chips.

All definitions here specified are not tested, only the "generic" part and ksz8051 part.  It is only rewrite from scratch from the datasheet.

Register definitions BCR BSR ID1 ID2 ANTX ANRX ANEXP ANNPTX ANNPRX are standardized and common for all PHYs I learned. Currently they are defined in each PHY family but it can be changed.

The problem in phy register definitions is that they have not standardized names, the names that I made are shorten version of the register name sentences found in datasheet. The names can be changed when some shorts are not self-descriptive.

This PR doesn't touch anything, when users look at them and agreed that it is good to go, it should be in master soon.
Is this enough? I would expect to see LINK_DOWN, LINK_HD_10M, LINK_FD_10M, LINK_HD_100M, LINK_FD_100M, LINK_HD_1000M, LINK_FD_1000M

To cover the link being up for 10, 100, or 1000 base T and full duplex or half duplex.