Merge pull request #1905 from nfi/compiler-warnings-cc2538

Fixed compiler warnings for CC2538-based platforms

cpu/cc2538/dev/ecc-algorithm.c

@@ -40,6 +40,7 @@
 
 #include <limits.h>
 #include <stdio.h>
+#include <string.h>
 
 #include "dev/ecc-algorithm.h"
 #include "dev/ecc-driver.h"

cpu/cc2538/ieee-addr.c

@@ -40,6 +40,7 @@
 #include "ieee-addr.h"
 
 #include <stdint.h>
+#include <string.h>
 /*---------------------------------------------------------------------------*/
 void
 ieee_addr_cpy_to(uint8_t *dst, uint8_t len)

cpu/cc253x/usb/common/cdc-acm/cdc-acm.c

@@ -4,6 +4,7 @@
 #include "usb-core.h"
 
 #include <stdio.h>
+#include <string.h>
 
 #ifdef DEBUG
 #define PRINTF(...) printf(__VA_ARGS__)