AP_ADC: ADS1115: coding style fixes

- Clean trailing whitespaces
  - Fix switch
  - Use pragma once

libraries/AP_ADC/AP_ADC_ADS1115.cpp

@@ -88,15 +88,14 @@
 #define error(fmt, args ...)
 #endif
 
-extern const AP_HAL::HAL& hal;
+extern const AP_HAL::HAL &hal;
 
 #define ADS1115_CHANNELS_COUNT           6
 
 const uint8_t AP_ADC_ADS1115::_channels_number  = ADS1115_CHANNELS_COUNT;
 
 /* Only two differential channels used */
-static const uint16_t mux_table[ADS1115_CHANNELS_COUNT] = 
-{
+static const uint16_t mux_table[ADS1115_CHANNELS_COUNT] = {
     ADS1115_MUX_P1_N3,
     ADS1115_MUX_P2_N3,
     ADS1115_MUX_P0_NG,

libraries/AP_ADC/AP_ADC_ADS1115.h

@@ -1,7 +1,5 @@
 /// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
-#ifndef __AP_ADC_ADS1115_H__
-#define __AP_ADC_ADS1115_H__
-
+#pragma once
 
 #include <inttypes.h>
 #include "AP_ADC.h"
@@ -43,5 +41,3 @@ private:
 
     float _convert_register_data_to_mv(int16_t word) const;
 };
-
-#endif