AP_RangeFinder: Clarify the purpose of input registers

libraries/AP_RangeFinder/AP_RangeFinder_LeddarOne.cpp

@@ -164,11 +164,10 @@ bool AP_RangeFinder_LeddarOne::CRC16(uint8_t *aBuffer, uint8_t aLength, bool aCh
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       0: slave address (LEDDARONE_DEFAULT_ADDRESS)
       1: functions code
-      2: ?
+      2: byte count
-3-4-5-6: timestamp
+5-6-3-4: timestamp
     7-8: internal temperature
-      9: ?
+   9-10: number of detections
-     10: number of detections
   11-12: first distance
   13-14: first amplitude
   15-16: second distance