adf435x: shuffle register description table

adf435x: shuffle register description table

Move table columns, put the bit field position to the front before the
name to get a less fragile visual appearance. All fields have a position
and a name (of variable length), some of them have a "parser" (actually
a formatter for their content).

Address Python style while we are here: Prefer tuples over lists for
immutable data. Add trailing commas to reduce future diff sizes.

Add a TODO comment about optional content checkers. The current decoder
implementation lets invalid register data pass unnoticed.

[ see a word diff for the commit's essence ]