Add missing <malloc.h> and <string.h> includes.

Change-Id: Ia41756e607663d056e7d2fdd7ecbec7e5841a913
diff --git a/fastbootd/utils.c b/fastbootd/utils.c
index a9ab47e..4c3a2e8 100644
--- a/fastbootd/utils.c
+++ b/fastbootd/utils.c
@@ -36,6 +36,7 @@
 #include <sys/ioctl.h>
 #include <linux/fs.h>
 #include <stdlib.h>
+#include <string.h>
 #include <cutils/properties.h>
 
 #include "utils.h"