test: list: Add tests for hexdump.c

Add tests for the hex2bin, bin2hex, and hex_to_bin functions, which were
recently added to U-Boot.

Signed-off-by: Mario Six <mario.six@gdsys.cc>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/test/lib/Makefile b/test/lib/Makefile
new file mode 100644
index 0000000..ea68fae
--- /dev/null
+++ b/test/lib/Makefile
@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0+
+#
+# (C) Copyright 2018
+# Mario Six, Guntermann & Drunck GmbH, mario.six@gdsys.cc
+obj-y += hexdump.o