Include missing <string.h>

c/src/libchip/flash/am29lv160.c

@@ -11,6 +11,7 @@
 
 #include <stdio.h>
 #include <errno.h>
+#include <string.h>
 
 #include <rtems.h>
 

c/src/libchip/i2c/spi-sd-card.c

@@ -18,6 +18,7 @@
  */
 
 #include <stdio.h>
+#include <string.h>
 #include <errno.h>
 #include <inttypes.h>
 

c/src/libchip/rtc/ds1375.c

@@ -58,6 +58,7 @@
 #include <sys/fcntl.h>
 #include <errno.h>
 #include <stdio.h>
+#include <string.h>
 #include <inttypes.h>