rtw88: rtw8822c: Remove unused variable 'corr_val'

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

 drivers/net/wireless/realtek/rtw88/rtw8822c.c: In function ‘rtw8822c_dpk_dc_corr_check’:
 drivers/net/wireless/realtek/rtw88/rtw8822c.c:2445:5: warning: variable ‘corr_val’ set but not used [-Wunused-but-set-variable]

Cc: Yan-Hsuan Chuang <yhchuang@realtek.com>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
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/20201102112410.1049272-39-lee.jones@linaro.org
Link: https://lore.kernel.org/r/20201102112410.1049272-39-lee.jones@linaro.org

drivers/net/wireless/realtek/rtw88/rtw8822c.c

@@ -2442,7 +2442,7 @@ static void rtw8822c_dpk_rxbb_dc_cal(struct rtw_dev *rtwdev, u8 path)
 static u8 rtw8822c_dpk_dc_corr_check(struct rtw_dev *rtwdev, u8 path)
 {
 	u16 dc_i, dc_q;
-	u8 corr_val, corr_idx;
+	u8 corr_idx;
 
 	rtw_write32(rtwdev, REG_RXSRAM_CTL, 0x000900f0);
 	dc_i = (u16)rtw_read32_mask(rtwdev, REG_STAT_RPT, GENMASK(27, 16));
@@ -2455,7 +2455,7 @@ static u8 rtw8822c_dpk_dc_corr_check(struct rtw_dev *rtwdev, u8 path)
 
 	rtw_write32(rtwdev, REG_RXSRAM_CTL, 0x000000f0);
 	corr_idx = (u8)rtw_read32_mask(rtwdev, REG_STAT_RPT, GENMASK(7, 0));
-	corr_val = (u8)rtw_read32_mask(rtwdev, REG_STAT_RPT, GENMASK(15, 8));
+	rtw_read32_mask(rtwdev, REG_STAT_RPT, GENMASK(15, 8));
 
 	if (dc_i > 200 || dc_q > 200 || corr_idx < 40 || corr_idx > 65)
 		return 1;