post: Migrate to Kconfig

We move the existing CONFIG_POST_* functionality over to CFG_POST and
then introduce CONFIG_POST to Kconfig.

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/test/Kconfig b/test/Kconfig
index a6b463e..9f4641a 100644
--- a/test/Kconfig
+++ b/test/Kconfig
@@ -1,3 +1,8 @@
+config POST
+	bool "Power On Self Test support"
+	help
+	  See doc/README.POST for more details
+
 menuconfig UNIT_TEST
 	bool "Unit tests"
 	help