FROMLIST: wifi: ath12k: fix incorrect channel survey index

A wrong channel survey index was introduced in
ath12k_mac_op_get_survey by [1], which can cause ACS to fail.

The index is decremented before being used, resulting in an
incorrect value when accessing the channel survey data.

Fix the index handling to ensure the correct survey entry is
used and avoid ACS failures.

Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.1.c5-00302-QCAHMTSWPL_V1.0_V2.0_SILICONZ-1.115823.3

Fixes: 4f242b1 ("wifi: ath12k: support get_survey mac op for single wiphy") # [1]
Signed-off-by: Yingying Tang <yingying.tang@oss.qualcomm.com>
Signed-off-by: Miaoqing Pan <miaoqing.pan@oss.qualcomm.com>
Link: https://lore.kernel.org/linux-wireless/20260210024440.3422264-1-yingying.tang@oss.qualcomm.com/

Author: MilanoPipo

drivers/net/wireless/ath/ath12k/mac.c

@@ -13162,6 +13162,7 @@ int ath12k_mac_op_get_survey(struct ieee80211_hw *hw, int idx,
 	struct ath12k *ar;
 	struct ieee80211_supported_band *sband;
 	struct survey_info *ar_survey;
+	int orig_idx = idx;
 
 	lockdep_assert_wiphy(hw->wiphy);
 
@@ -13196,7 +13197,7 @@ int ath12k_mac_op_get_survey(struct ieee80211_hw *hw, int idx,
 		return -ENOENT;
 	}
 
-	ar_survey = &ar->survey[idx];
+	ar_survey = &ar->survey[orig_idx];
 
 	ath12k_mac_update_bss_chan_survey(ar, &sband->channels[idx]);