ath5k: fix antenna div gc for <= AR5K_SREV_PHY_2413

In commit 39d5b2c8 "ath5k: update
AR5K_PHY_RESTART_DIV_GC values to match masks" i introduced a regression on PHY
chips older than AR5K_SREV_PHY_5413, which caused signal values to be about
10dB less that before. This patch reverts the AR5K_PHY_RESTART_DIV_GC values to
the same values which were effectively used before (without the bitmask
mistake). This brings signal levels back to normal on these PHY chips.
Signed-off-by: NBruno Randolf <br1@einfach.org>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath5k/phy.c

@@ -1768,7 +1768,7 @@ ath5k_hw_set_fast_div(struct ath5k_hw *ah, u8 ee_mode, bool enable)
 
 	if (enable) {
 		AR5K_REG_WRITE_BITS(ah, AR5K_PHY_RESTART,
-				AR5K_PHY_RESTART_DIV_GC, 1);
+				AR5K_PHY_RESTART_DIV_GC, 4);
 
 		AR5K_REG_ENABLE_BITS(ah, AR5K_PHY_FAST_ANT_DIV,
 					AR5K_PHY_FAST_ANT_DIV_EN);