p54: clamp properly instead of just truncating

The call to clamp_t() first truncates the variable signed 8 bit and as a
result, the actual clamp is a no-op.

Fixes: 0d78156eef1d ('p54: improve site survey')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/p54/txrx.c

@@ -586,7 +586,7 @@ static void p54_rx_stats(struct p54_common *priv, struct sk_buff *skb)
 	chan = priv->curchan;
 	if (chan) {
 		struct survey_info *survey = &priv->survey[chan->hw_value];
-		survey->noise = clamp_t(s8, priv->noise, -128, 127);
+		survey->noise = clamp(priv->noise, -128, 127);
 		survey->channel_time = priv->survey_raw.active;
 		survey->channel_time_tx = priv->survey_raw.tx;
 		survey->channel_time_busy = priv->survey_raw.tx +