cpu/sam21_common: remove define of LITTLE_ENDIAN

This define conflicts with LITTLE_ENDIAN defined in
include/machine/endian.h which is part of gcc-arm-none-eabi.

Also, the define does not seem to be used by the ASF included files.

cpu/sam21_common/include/cmsis/samr21/README.md

@@ -13,3 +13,15 @@ the trailing white space had to be removed.  Please take this into account
 when comparing to the original ASF distribution.
 
     find include/ -name '*.h' -exec sed -i 's/\s*$//' '{}' +
+
+## LITTLE_ENDIAN
+
+These include files define `LITTLE_ENDIAN`.  But we think this is wrong.  It
+seems more logical to let the compiler decide in which mode the ARM code is
+to be translated.  In include/machine/endian.h there is already a define of
+`LITTLE_ENDIAN` (and `BIG_ENDIAN`) for a different purpose.
+
+So, we decided to remove the define from the ASF CMSIS files.  The command
+for it (running from this directory) is:
+
+    find include/ -name '*.h' -exec sed -i '/^#define\s\s*LITTLE_ENDIAN/d' '{}' +

cpu/sam21_common/include/cmsis/samr21/include/samr21e16a.h

@@ -229,7 +229,6 @@ void I2S_Handler                 ( void );
  * \brief Configuration of the Cortex-M0+ Processor and Core Peripherals
  */
 
-#define LITTLE_ENDIAN          1
 #define __CM0PLUS_REV          1         /*!< Core revision r0p1 */
 #define __MPU_PRESENT          0         /*!< MPU present or not */
 #define __NVIC_PRIO_BITS       2         /*!< Number of bits used for Priority Levels */

cpu/sam21_common/include/cmsis/samr21/include/samr21e17a.h

@@ -229,7 +229,6 @@ void I2S_Handler                 ( void );
  * \brief Configuration of the Cortex-M0+ Processor and Core Peripherals
  */
 
-#define LITTLE_ENDIAN          1
 #define __CM0PLUS_REV          1         /*!< Core revision r0p1 */
 #define __MPU_PRESENT          0         /*!< MPU present or not */
 #define __NVIC_PRIO_BITS       2         /*!< Number of bits used for Priority Levels */

cpu/sam21_common/include/cmsis/samr21/include/samr21e18a.h

@@ -229,7 +229,6 @@ void I2S_Handler                 ( void );
  * \brief Configuration of the Cortex-M0+ Processor and Core Peripherals
  */
 
-#define LITTLE_ENDIAN          1
 #define __CM0PLUS_REV          1         /*!< Core revision r0p1 */
 #define __MPU_PRESENT          0         /*!< MPU present or not */
 #define __NVIC_PRIO_BITS       2         /*!< Number of bits used for Priority Levels */

cpu/sam21_common/include/cmsis/samr21/include/samr21g16a.h

@@ -229,7 +229,6 @@ void I2S_Handler                 ( void );
  * \brief Configuration of the Cortex-M0+ Processor and Core Peripherals
  */
 
-#define LITTLE_ENDIAN          1
 #define __CM0PLUS_REV          1         /*!< Core revision r0p1 */
 #define __MPU_PRESENT          0         /*!< MPU present or not */
 #define __NVIC_PRIO_BITS       2         /*!< Number of bits used for Priority Levels */

cpu/sam21_common/include/cmsis/samr21/include/samr21g17a.h

@@ -229,7 +229,6 @@ void I2S_Handler                 ( void );
  * \brief Configuration of the Cortex-M0+ Processor and Core Peripherals
  */
 
-#define LITTLE_ENDIAN          1
 #define __CM0PLUS_REV          1         /*!< Core revision r0p1 */
 #define __MPU_PRESENT          0         /*!< MPU present or not */
 #define __NVIC_PRIO_BITS       2         /*!< Number of bits used for Priority Levels */

cpu/sam21_common/include/cmsis/samr21/include/samr21g18a.h

@@ -229,7 +229,6 @@ void I2S_Handler                 ( void );
  * \brief Configuration of the Cortex-M0+ Processor and Core Peripherals
  */
 
-#define LITTLE_ENDIAN          1
 #define __CM0PLUS_REV          1         /*!< Core revision r0p1 */
 #define __MPU_PRESENT          0         /*!< MPU present or not */
 #define __NVIC_PRIO_BITS       2         /*!< Number of bits used for Priority Levels */