INS: add get_accel_health_all and get_gyro_health_all

Returns true only if all available accels or gyros are healthy

libraries/AP_InertialSensor/AP_InertialSensor.cpp

@@ -294,6 +294,30 @@ AP_InertialSensor::init_gyro()
     _save_parameters();
 }
 
+// get_gyro_health_all - return true if all gyros are healthy
+bool AP_InertialSensor::get_gyro_health_all(void) const
+{
+    for (uint8_t i=0; i<get_gyro_count(); i++) {
+        if (!get_gyro_health(i)) {
+            return false;
+        }
+    }
+    // return true if we have at least one gyro
+    return (get_gyro_count() > 0);
+}
+
+// get_accel_health_all - return true if all accels are healthy
+bool AP_InertialSensor::get_accel_health_all(void) const
+{
+    for (uint8_t i=0; i<get_accel_count(); i++) {
+        if (!get_accel_health(i)) {
+            return false;
+        }
+    }
+    // return true if we have at least one accel
+    return (get_accel_count() > 0);
+}
+
 void
 AP_InertialSensor::_init_accel()
 {

libraries/AP_InertialSensor/AP_InertialSensor.h

@@ -118,10 +118,12 @@ public:
     // multi-device interface
     virtual bool get_gyro_health(uint8_t instance) const { return true; }
     bool get_gyro_health(void) const { return get_gyro_health(_get_primary_gyro()); }
+    bool get_gyro_health_all(void) const;
     virtual uint8_t get_gyro_count(void) const { return 1; };
 
     virtual bool get_accel_health(uint8_t instance) const { return true; }
     bool get_accel_health(void) const { return get_accel_health(get_primary_accel()); }
+    bool get_accel_health_all(void) const;
     virtual uint8_t get_accel_count(void) const { return 1; };
 
     // get accel offsets in m/s/s