ath9k_hw: min_t() casts u32 to int

The code here treats very large values of "limit" as less than
MAX_POWER_RATE because of the cast to int.  We should do the compare
as u32 instead.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Pavel Roskin <proski@gnu.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/hw.c

@@ -2579,7 +2579,7 @@ void ath9k_hw_set_txpowerlimit(struct ath_hw *ah, u32 limit, bool test)
 	struct ath9k_channel *chan = ah->curchan;
 	struct ieee80211_channel *channel = chan->chan;
 
-	reg->power_limit = min_t(int, limit, MAX_RATE_POWER);
+	reg->power_limit = min_t(u32, limit, MAX_RATE_POWER);
 	if (test)
 		channel->max_power = MAX_RATE_POWER / 2;