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/kmcoge5ne_defconfig b/configs/kmcoge5ne_defconfig
index c2a17c6..013277c 100644
--- a/configs/kmcoge5ne_defconfig
+++ b/configs/kmcoge5ne_defconfig
@@ -243,3 +243,4 @@
 CONFIG_QE=y
 CONFIG_SYS_NS16550=y
 CONFIG_BCH=y
+CONFIG_POST=y