ath9k_hw: turn a few big macros into functions

RF_BANK_SETUP, REG_WRITE_RF_ARRAY and REG_WRITE_ARRAY are way too big,
so they shouldn't be inlined at every single callsite, especially since they
can easily be turned into real functions.

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