Some PHYs can be heavily modified between revisions, and the addresses of
the registers are changed and the register fields are moved from one
register to another.
To integrate more PHYs in the same driver with the same register fields,
but these register fields were located in different registers at
different offsets, I introduced the phy_reg_fied structure.
phy_reg_fied structure abstracts the register fields differences.
Signed-off-by: Radu Pirea (OSS) <radu-nicolae.pirea@xxxxxxxxxxx>