ath9k_hw: allow for spliting up ANI operations by family

The AR9003 hardware family will use a slightly modified ANI
implementation which has not yet been tested on the other hardware
families. To allow for this new ANI implementation a few ANI
calls need to be abstracted away. This patch just allows for
each hardware family to declare their own ANI ops and annotates
the current ANI implementation as old.

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