AR9287 EEPROM layout.
The AR9287 only supports 2ghz, so I've removed the 5ghz code (but left
the 5ghz edge flags in there for now) and hard-coded the 2ghz-only
path.
Whilst I'm there, fix a typo (ar9285->ar9287.)
This meets basic TX throughput testing - iperf TX tests == 27-28mbit in 11g,
matching the rest of my 11g kit.