AP_RangeFinder: Rework function structure in TeraRanger driver

libraries/AP_RangeFinder/AP_RangeFinder_TeraRangerI2C.cpp

@@ -137,17 +137,16 @@ bool AP_RangeFinder_TeraRangerI2C::process_raw_measure(uint16_t raw_distance, ui
   if (raw_distance == 0xFFFF) {
       // Too far away
       return false;
-  }
-  if (raw_distance == 0x0000) {
+  } else if (raw_distance == 0x0000) {
       // Too close
       return false;
-  }
-  if (raw_distance == 0x0001) {
+  } else if (raw_distance == 0x0001) {
       // Unable to measure
       return false;
+  } else {
+    output_distance_cm = raw_distance/10; // Conversion to centimeters
+    return true;
   }
-  output_distance_cm = raw_distance/10;
-  return true;
 }
 
 /*