mac80211: ath9k: Increase allowed antenna gain to 6 dBi

FCC allows maximum antenna gain of 6 dBi. 15.247(b)(4):

> (4) The conducted output power limit
> specified in paragraph (b) of this section
> is based on the use of antennas
> with directional gains that do not exceed
> 6 dBi. Except as shown in paragraph
> (c) of this section, if transmitting
> antennas of directional gain greater
> than 6 dBi are used, the conducted
> output power from the intentional radiator
> shall be reduced below the stated
> values in paragraphs (b)(1), (b)(2),
> and (b)(3) of this section, as appropriate,
> by the amount in dB that the
> directional gain of the antenna exceeds
> 6 dBi.

Signed-off-by: Sven Eckelmann <sven@narfation.org>

package/kernel/mac80211/patches/ath/365-ath9k-adjust-tx-power-reduction-for-US-regulatory-do.patch

@@ -3,7 +3,7 @@ Date: Wed, 19 Jul 2017 08:49:31 +0200
 Subject: [PATCH] ath9k: adjust tx power reduction for US regulatory
  domain
 
-FCC regulatory rules allow for up to 3 dBi antenna gain. Account for
+FCC regulatory rules allow for up to 6 dBi antenna gain. Account for
 this in the EEPROM based tx power reduction code.
 
 Signed-off-by: Felix Fietkau <nbd@nbd.name>
@@ -15,9 +15,9 @@ Signed-off-by: Felix Fietkau <nbd@nbd.name>
  	if (ant_gain > max_gain)
  		ant_reduction = ant_gain - max_gain;
  
-+	/* FCC allows maximum antenna gain of 3 dBi */
++	/* FCC allows maximum antenna gain of 6 dBi */
 +	if (reg->region == NL80211_DFS_FCC)
-+		ant_reduction = max_t(int, ant_reduction - 6, 0);
++		ant_reduction = max_t(int, ant_reduction - 12, 0);
 +
  	ah->eep_ops->set_txpower(ah, chan, ctl,
  				 ant_reduction, new_pwr, test);