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/pg_wcom_seli8_defconfig b/configs/pg_wcom_seli8_defconfig
index ad08e35..8311b3a 100644
--- a/configs/pg_wcom_seli8_defconfig
+++ b/configs/pg_wcom_seli8_defconfig
@@ -100,3 +100,4 @@
 CONFIG_SPECIFY_CONSOLE_INDEX=y
 CONFIG_DM_SERIAL=y
 CONFIG_SYS_NS16550=y
+CONFIG_POST=y