selfboot: store bounce buffer in struct payload

In order to break the dependency on selfboot for jumping to
payload the bounce buffer location needs to be communicated.
Therefore, add the bounce buffer to struct payload.

Change-Id: I9d9396e5c5bfba7a63940227ee0bdce6cba39578
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/5299
Tested-by: build bot (Jenkins)
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/include/payload_loader.h

@@ -22,14 +22,16 @@
 #include <stdint.h>
 #include <stddef.h>
 
-struct payload_backing_store {
+struct buffer_area {
 	void *data;
 	size_t size;
 };
 
 struct payload {
 	const char *name;
-	struct payload_backing_store backing_store;
+	struct buffer_area backing_store;
+	/* Used when payload wants memory coreboot ramstage is running at. */
+	struct buffer_area bounce;
 	void *entry;
 };