rtlwifi: phy: Remove set but unused variable 'bbvalue'

Fixes the following W=1 kernel build warning(s):

 drivers/net/wireless/realtek/rtlwifi/rtl8723ae/phy.c: In function ‘_rtl8723e_phy_iq_calibrate’:
 drivers/net/wireless/realtek/rtlwifi/rtl8723ae/phy.c:1150:6: warning: variable ‘bbvalue’ set but not used [-Wunused-but-set-variable]

Cc: Ping-Ke Shih <pkshih@realtek.com>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Larry Finger <Larry.Finger@lwfinger.net>
Cc: linux-wireless@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20201102112410.1049272-27-lee.jones@linaro.org

drivers/net/wireless/realtek/rtlwifi/rtl8723ae/phy.c

@@ -1147,10 +1147,8 @@ static void _rtl8723e_phy_iq_calibrate(struct ieee80211_hw *hw,
 
 	const u32 retrycount = 2;
 
-	u32 bbvalue;
-
 	if (t == 0) {
-		bbvalue = rtl_get_bbreg(hw, 0x800, MASKDWORD);
+		rtl_get_bbreg(hw, 0x800, MASKDWORD);
 
 		rtl8723_save_adda_registers(hw, adda_reg,
 					    rtlphy->adda_backup, 16);