RangeFinder: remove raw_value from SharpGP2Y

libraries/AP_RangeFinder/AP_RangeFinder_SharpGP2Y.h

@@ -10,11 +10,11 @@ class AP_RangeFinder_SharpGP2Y : public RangeFinder
 {
 public:
     AP_RangeFinder_SharpGP2Y(AP_HAL::AnalogSource *source, FilterInt16 *filter);
-    int  convert_raw_to_distance(int _raw_value) {
-        if( _raw_value == 0 ) {
+    int16_t convert_raw_to_distance(int16_t raw_value) {
+        if (raw_value == 0) {
             return max_distance;
         } else {
-            return 14500/_raw_value;
+            return 14500/raw_value;
         }
     }       // read value from analog port and return distance in cm