SRV_Channel: fix get_output_norm comment

also minor formatting fix

libraries/SRV_Channel/SRV_Channel.cpp

@@ -171,7 +171,7 @@ float SRV_Channel::get_output_norm(void)
         ret = 0;
     }
     if (get_reversed()) {
-           ret = -ret;
+        ret = -ret;
     }
     return ret;
 }

libraries/SRV_Channel/SRV_Channel.h

@@ -277,7 +277,7 @@ private:
     // return PWM for a given limit value
     uint16_t get_limit_pwm(Limit limit) const;
 
-    // get normalised output from -1 to 1
+    // get normalised output from -1 to 1, assuming 0 at mid point of servo_min/servo_max
     float get_output_norm(void);
 
     // a bitmask type wide enough for NUM_SERVO_CHANNELS
@@ -337,8 +337,8 @@ public:
     // get pwm output for the first channel of the given function type.
     static bool get_output_pwm(SRV_Channel::Aux_servo_function_t function, uint16_t &value);
 
-    // get normalised output (-1 to 1 for angle, 0 to 1 for range). Value is taken from pwm value
-    // return zero on error.
+    // get normalised output (-1 to 1 with 0 at mid point of servo_min/servo_max)
+    // Value is taken from pwm value.  Returns zero on error.
     static float get_output_norm(SRV_Channel::Aux_servo_function_t function);
 
     // get output channel mask for a function