global: fix typo

global.c

@@ -20,6 +20,7 @@
 /* standard libraries */
 #include <stdint.h> // standard integer types
 #include <stdlib.h> // general utilities
+#include <string.h> // memory utilities
 
 /* STM32 (including CM3) libraries */
 #include <libopencmsis/core_cm3.h> // Cortex M3 utilities
@@ -31,7 +32,6 @@
 #include <libopencm3/stm32/exti.h> // external interrupt defines
 
 #include "global.h" // common methods
-#include "string.h" // memory utilities
 
 volatile bool button_flag = false;
 volatile uint32_t sleep_duration = 0; /**< sleep duration count down (in SysTick interrupts) */