carl9170: allow users to lower output power level

This patch implements a simple way of reducing the
output power of the device by a configurable upper
limit.

Requested-by: Harshal Chhaya <harshal@gmail.com>
Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/carl9170/carl9170.h

@@ -559,6 +559,7 @@ int carl9170_set_hwretry_limit(struct ar9170 *ar, const u32 max_retry);
 int carl9170_upload_key(struct ar9170 *ar, const u8 id, const u8 *mac,
 	const u8 ktype, const u8 keyidx, const u8 *keydata, const int keylen);
 int carl9170_disable_key(struct ar9170 *ar, const u8 id);
+int carl9170_set_mac_tpc(struct ar9170 *ar, struct ieee80211_channel *channel);
 
 /* RX */
 void carl9170_rx(struct ar9170 *ar, void *buf, unsigned int len);