ath9k_hw: distinguish single-chip solutions on initial probe print

Devices with external radios have revisions which we can count on.
On single chip solutions these EEPROM values for these radio revision
also exist but are not meaningful as the radios are embedded onto the
same chip. Each single-chip device evolves together as one device.

Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>