ath9k_hw: fix fast clock handling for 5GHz channels

Combine multiple checks that were supposed to check for the same
conditions, but didn't. Always enable fast PLL clock on AR9280 2.0

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