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/post/lib_powerpc/threei.c b/post/lib_powerpc/threei.c
index f49c85e..ec52d23 100644
--- a/post/lib_powerpc/threei.c
+++ b/post/lib_powerpc/threei.c
@@ -21,7 +21,7 @@
 #include <post.h>
 #include "cpu_asm.h"
 
-#if CONFIG_POST & CONFIG_SYS_POST_CPU
+#if CFG_POST & CONFIG_SYS_POST_CPU
 
 extern void cpu_post_exec_21 (ulong *code, ulong *cr, ulong *res, ulong op);
 extern ulong cpu_post_makecr (long v);