b43: fix extpa_gain check for 2GHz

On the 2GHz and and on the 5GHZ band only the extpa_gain setting from
the 5GHz band was checked. this patch makes it check the property from
the correct band.
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/b43/tables_nphy.c

@@ -3728,7 +3728,7 @@ const u32 *b43_nphy_get_tx_gain_table(struct b43_wldev *dev)
 		switch (phy->rev) {
 		case 6:
 		case 5:
-			if (sprom->fem.ghz5.extpa_gain == 3)
+			if (sprom->fem.ghz2.extpa_gain == 3)
 				return b43_ntab_tx_gain_epa_rev3_hi_pwr_2g;
 			/* fall through */
 		case 4: