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/configs/kmcent2_defconfig b/configs/kmcent2_defconfig
index 48ac85b..41b2628 100644
--- a/configs/kmcent2_defconfig
+++ b/configs/kmcent2_defconfig
@@ -110,3 +110,4 @@
 CONFIG_BCH=y
 CONFIG_PANIC_HANG=y
 CONFIG_LZO=y
+CONFIG_POST=y