Add comment about IC-756 data mode

rigs/icom/icom.c

@@ -1575,7 +1575,9 @@ int icom_set_mode_with_data(RIG *rig, vfo_t vfo, rmode_t mode,
 
     switch (mode)
     {
-    case RIG_MODE_PKTUSB:
+    case RIG_MODE_PKTUSB: 
+        // xFE xFE x6E xE0 x1A x06 x01 xFD switchs mod input from MIC to ACC
+        // This apparently works for IC-756ProIII but nobody has asked for it yet
         icom_mode = RIG_MODE_USB;
         break;