ath9k_hw: clean up duplicate and unnused eeprom related defines

AR*_MAX_RATE_POWER => MAX_RATE_POWER
AR*_EEPROM_MODAL_SPURS => AR_EEPROM_MODAL_SPURS
AR*_OPFLAGS_* => AR5416_OPFLAGS_*
...

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