AP_Airspeed: added ARSPD_OPTIONS bit for disabling voltage correction

if the MS4525 has its own LDO then we are should disable the
correction

libraries/AP_Airspeed/AP_Airspeed.cpp

@@ -168,7 +168,7 @@ const AP_Param::GroupInfo AP_Airspeed::var_info[] = {
     // @Param: _OPTIONS
     // @DisplayName: Airspeed options bitmask
     // @Description: Bitmask of options to use with airspeed. Disable and/or re-enable sensor based on the difference between airspeed and ground speed based on ARSPD_WIND_MAX threshold, if set
-    // @Bitmask: 0:Disable sensor, 1:Re-enable sensor
+    // @Bitmask: 0:Disable sensor, 1:Re-enable sensor, 2:DisableVoltageCorrection
     // @User: Advanced
     AP_GROUPINFO("_OPTIONS", 21, AP_Airspeed, _options, OPTIONS_DEFAULT),
 

libraries/AP_Airspeed/AP_Airspeed.h

@@ -145,6 +145,7 @@ public:
     enum OptionsMask {
         ON_FAILURE_AHRS_WIND_MAX_DO_DISABLE                   = (1<<0),   // If set then use airspeed failure check
         ON_FAILURE_AHRS_WIND_MAX_RECOVERY_DO_REENABLE         = (1<<1),   // If set then automatically enable the airspeed sensor use when healthy again.
+        DISABLE_VOLTAGE_CORRECTION                            = (1<<2),
     };
 
     enum airspeed_type {

libraries/AP_Airspeed/AP_Airspeed_Backend.h

@@ -55,6 +55,11 @@ protected:
         return instance;
     }
 
+    // see if voltage correction should be disabled
+    bool disable_voltage_correction(void) const {
+        return (frontend._options.get() & AP_Airspeed::OptionsMask::DISABLE_VOLTAGE_CORRECTION) != 0;
+    }
+
     AP_Airspeed::pitot_tube_order get_tube_order(void) const {
         return AP_Airspeed::pitot_tube_order(frontend.param[instance].tube_order.get());
     }

libraries/AP_Airspeed/AP_Airspeed_MS4525.cpp

@@ -193,8 +193,10 @@ void AP_Airspeed_MS4525::_collect()
     float temp  = _get_temperature(dT_raw);
     float temp2 = _get_temperature(dT_raw2);
     
-    _voltage_correction(press, temp);
-    _voltage_correction(press2, temp2);
+    if (!disable_voltage_correction()) {
+        _voltage_correction(press, temp);
+        _voltage_correction(press2, temp2);
+    }
 
     WITH_SEMAPHORE(sem);