mac80211: fix tx power regression

Revert an accidental change that was introduced by having an old version
of the patch in my git tree, which was merged in 609208597b

Signed-off-by: Felix Fietkau <nbd@nbd.name>

package/kernel/mac80211/patches/315-ath9k-adjust-tx-power-reduction-for-US-regulatory-do.patch

@@ -17,7 +17,7 @@ Signed-off-by: Felix Fietkau <nbd@nbd.name>
  
 +	/* FCC allows maximum antenna gain of 3 dBi */
 +	if (reg->region == NL80211_DFS_FCC)
-+		ant_reduction = min_t(int, ant_reduction - 6, 0);
++		ant_reduction = max_t(int, ant_reduction - 6, 0);
 +
  	ah->eep_ops->set_txpower(ah, chan, ctl, ant_reduction, new_pwr, test);
  }