qcacld-3.0: Add declaration for btc_chain_mode_policy

The BTC_CHAIN_MODE command policy table is missing its declaration in the
.h file. Add the declaration to resolve the compilation issues.

Change-Id: I5bdd54dc9c3488054bafabd772f4f8b375fe50fa
CRs-Fixed: 2773241

core/hdd/src/wlan_hdd_btc_chain_mode.h

@@ -48,6 +48,9 @@ int wlan_hdd_cfg80211_set_btc_chain_mode(struct wiphy *wiphy,
 					 struct wireless_dev *wdev,
 					 const void *data, int data_len);
 
+extern const struct nla_policy
+btc_chain_mode_policy[QCA_VENDOR_ATTR_BTC_CHAIN_MODE_MAX + 1];
+
 #define FEATURE_BTC_CHAIN_MODE_COMMANDS					\
 {									\
 	.info.vendor_id = QCA_NL80211_VENDOR_ID,			\