fix:luat_bluetooth_mac_swap 编译警告

components/bluetooth/src/luat_bluetooth.c

@@ -6,7 +6,6 @@
 #define LUAT_LOG_TAG "bluetooth"
 
 void luat_bluetooth_mac_swap(uint8_t* mac){
-    uint8_t len = 0;
     uint8_t tmp_mac[LUAT_BLUETOOTH_MAC_LEN] = {0};
     memcpy(tmp_mac, mac, LUAT_BLUETOOTH_MAC_LEN);
     for(int i=0;i<LUAT_BLUETOOTH_MAC_LEN;i++){