test: Add hexdump.h to the unit test header

Since ut_asserteq_mem() uses bin2hex() we should include this header in
ut.h to avoid errors. Add it.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Wolfgang Wallner <wolfgang.wallner@br-automation.com>

include/test/ut.h

@@ -8,6 +8,7 @@
 #ifndef __TEST_UT_H
 #define __TEST_UT_H
 
+#include <hexdump.h>
 #include <linux/err.h>
 
 struct unit_test_state;