kconfig: Add API kconfig file

Add kconfig file to enable API support

Signed-off-by: Emmanuel Vadot <manu@bidouilliste.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/Kconfig b/Kconfig
index 0dd21df..81b4226 100644
--- a/Kconfig
+++ b/Kconfig
@@ -308,6 +308,8 @@
 
 endmenu		# Boot images
 
+source "api/Kconfig"
+
 source "common/Kconfig"
 
 source "cmd/Kconfig"