ath9k_hw: the eep_map is used only for AR9280 PCI card ini fixup

We can reorganize the code in such a way that eep_map can be removed,
which makes the code more clearer.

Signed-off-by: Senthil Balasubramanian <senthilkumar@atheros.com>
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>