ath9k_hw: fix and clean up PHY activation delay

The delay calculation is the same for all chips, however some parts of the
code missed the extra delay factor for half/quarter.
Clean up the code and move the delay calculation to a common place.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/hw.h b/drivers/net/wireless/ath/ath9k/hw.h
index 8c827a1..8535f76 100644
--- a/drivers/net/wireless/ath/ath9k/hw.h
+++ b/drivers/net/wireless/ath/ath9k/hw.h
@@ -923,6 +923,8 @@
 void ath9k_hw_setantenna(struct ath_hw *ah, u32 antenna);
 
 /* General Operation */
+void ath9k_hw_synth_delay(struct ath_hw *ah, struct ath9k_channel *chan,
+			  int hw_delay);
 bool ath9k_hw_wait(struct ath_hw *ah, u32 reg, u32 mask, u32 val, u32 timeout);
 void ath9k_hw_write_array(struct ath_hw *ah, struct ar5416IniArray *array,
 			  int column, unsigned int *writecnt);