layout: Make `struct layout_include_args` private to `layout.c`

Change-Id: Icbfee68e85429fe41db1cad6b99f25e9f30cd672
Signed-off-by: Nico Huber <nico.h@gmx.de>
Original-Reviewed-on: https://review.coreboot.org/c/flashrom/+/33545
Original-Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Original-Reviewed-by: Anastasia Klimchuk <aklm@chromium.org>
Original-Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
Original-Reviewed-by: Peter Marheine <pmarheine@chromium.org>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/72219
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/layout.c b/layout.c
index d2a2908..aeffcd7 100644
--- a/layout.c
+++ b/layout.c
@@ -28,6 +28,11 @@
 	struct romentry *head;
 };
 
+struct layout_include_args {
+	char *name;
+	struct layout_include_args *next;
+};
+
 static struct flashrom_layout *global_layout;
 
 struct flashrom_layout *get_global_layout(void)