1) Add comments so it's clear why we did things; this may prevent
someone (e.g. me) from sinking time into fixing things that
aren't broken and/or were done for reason.
2) Drop mdio 0 probe/register; we don't use ag1xx mdio bus 0.
3) Cosmetic reording of some code (tested) that makes the defintion
more clear.
Signed-off-by: Daniel F. Dickinson <cshored@thecshore.com>
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