[ath_hal] Add Jupiter 2.1 (AR9462 mac 640.3) support.

Turns out I wasn't even initialising or programming a lot of stuff
for the AR9462 2.1 chip. Oops.

This mostly gets it working. powersave scan results in some pretty
hilarious NFcal hangs and I don't see beacons reliably.
There are still some xlna gain tables missing that ath9k has; I'll
follow up with some fixes and then see if the QCAFN222 NIC I have
tests this path.

Tested:

• QCAFN222 NIC, STA mode, 2GHz and 5GHz