Add missing includes.

Change-Id: I06ea08400efa511e627be37a4fd70fbdfadea2e6
diff --git a/minui/graphics_adf.c b/minui/graphics_adf.c
index ac6d64e..289c3be 100644
--- a/minui/graphics_adf.c
+++ b/minui/graphics_adf.c
@@ -19,6 +19,7 @@
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <unistd.h>
 
 #include <sys/cdefs.h>