Apply #ifdef/#ifndef where possible

Marlin/src/HAL/HAL_DUE/usb/compiler.h

@@ -230,7 +230,7 @@
 
 /* Define NO_INIT attribute */
 #if 0 //ndef NO_INIT
-#if defined   ( __CC_ARM   )
+#ifdef __CC_ARM
 #   define NO_INIT __attribute__((zero_init))
 #elif defined ( __ICCARM__ )
 #   define NO_INIT __no_init
@@ -262,7 +262,7 @@
 //! @{
 typedef unsigned char           Bool; //!< Boolean.
 #ifndef __cplusplus
-#if !defined(__bool_true_false_are_defined)
+#ifndef __bool_true_false_are_defined
 typedef unsigned char           bool; //!< Boolean.
 #endif
 #endif
@@ -443,7 +443,7 @@ typedef struct
 #define DISABLE   0
 #define ENABLE    1
 #ifndef __cplusplus
-#if !defined(__bool_true_false_are_defined)
+#ifndef __bool_true_false_are_defined
 #define false 0
 #define true 1
 #endif

Marlin/src/HAL/HAL_DUE/usb/osc.h

@@ -61,27 +61,27 @@ extern "C" {
  * Below BOARD_XXX macros are related to the specific board, and
  * should be defined by the board code, otherwise default value are used.
  */
-#if !defined(BOARD_FREQ_SLCK_XTAL)
+#ifndef BOARD_FREQ_SLCK_XTAL
 #  warning The board slow clock xtal frequency has not been defined.
 #  define BOARD_FREQ_SLCK_XTAL      (32768UL)
 #endif
 
-#if !defined(BOARD_FREQ_SLCK_BYPASS)
+#ifndef BOARD_FREQ_SLCK_BYPASS
 #  warning The board slow clock bypass frequency has not been defined.
 #  define BOARD_FREQ_SLCK_BYPASS    (32768UL)
 #endif
 
-#if !defined(BOARD_FREQ_MAINCK_XTAL)
+#ifndef BOARD_FREQ_MAINCK_XTAL
 #  warning The board main clock xtal frequency has not been defined.
 #  define BOARD_FREQ_MAINCK_XTAL    (12000000UL)
 #endif
 
-#if !defined(BOARD_FREQ_MAINCK_BYPASS)
+#ifndef BOARD_FREQ_MAINCK_BYPASS
 #  warning The board main clock bypass frequency has not been defined.
 #  define BOARD_FREQ_MAINCK_BYPASS  (12000000UL)
 #endif
 
-#if !defined(BOARD_OSC_STARTUP_US)
+#ifndef BOARD_OSC_STARTUP_US
 #  warning The board main clock xtal startup time has not been defined.
 #  define BOARD_OSC_STARTUP_US      (15625UL)
 #endif

Marlin/src/HAL/HAL_DUE/usb/spc_protocol.h

@@ -43,12 +43,12 @@
  * \asf_license_stop
  *
  */
+
 /*
  * Support and FAQ: visit <a href="http://www.atmel.com/design-support/">Atmel Support</a>
  */
-#ifndef  _SPC_PROTOCOL_H_
-#define  _SPC_PROTOCOL_H_
-
+#ifndef _SPC_PROTOCOL_H_
+#define _SPC_PROTOCOL_H_
 
 /**
  * \ingroup usb_msc_protocol

Marlin/src/HAL/HAL_DUE/usb/udi_cdc.h

@@ -55,7 +55,7 @@
 #include "udi.h"
 
 // Check the number of port
-#ifndef  UDI_CDC_PORT_NB
+#ifndef UDI_CDC_PORT_NB
 # define  UDI_CDC_PORT_NB 1
 #endif
 #if (UDI_CDC_PORT_NB < 1) || (UDI_CDC_PORT_NB > 7)

Marlin/src/HAL/HAL_DUE/usb/udi_cdc_conf.h

@@ -50,7 +50,7 @@
 #include "usb_protocol_cdc.h"
 #include "conf_usb.h"
 
-#ifndef  UDI_CDC_PORT_NB
+#ifndef UDI_CDC_PORT_NB
 # define  UDI_CDC_PORT_NB 1
 #endif
 

Marlin/src/HAL/HAL_STM32F1/SPI.h

@@ -58,7 +58,7 @@
 #define SPI_2XCLOCK_MASK 0x01  // SPI2X = bit 0 on SPSR
 
 // define SPI_AVR_EIMSK for AVR boards with external interrupt pins
-#if defined(EIMSK)
+#ifdef EIMSK
   #define SPI_AVR_EIMSK EIMSK
 #elif defined(GICR)
   #define SPI_AVR_EIMSK GICR