ath9k: Remove all the useless ah_ variable prefixes

drivers/net/wireless/ath9k/ani.c

drivers/net/wireless/ath9k/ani.h

drivers/net/wireless/ath9k/ath9k.h

drivers/net/wireless/ath9k/beacon.c

drivers/net/wireless/ath9k/calib.c

drivers/net/wireless/ath9k/calib.h

drivers/net/wireless/ath9k/eeprom.c

drivers/net/wireless/ath9k/eeprom.h

drivers/net/wireless/ath9k/hw.c

drivers/net/wireless/ath9k/hw.h

drivers/net/wireless/ath9k/mac.c

drivers/net/wireless/ath9k/main.c

drivers/net/wireless/ath9k/pci.c

drivers/net/wireless/ath9k/phy.c

drivers/net/wireless/ath9k/phy.h

drivers/net/wireless/ath9k/rc.c

drivers/net/wireless/ath9k/recv.c

drivers/net/wireless/ath9k/xmit.c