payloads/external/Makefile.inc: Clean up makefile

- Add comments dividing the payload sections.
- Move separate TINT and Memtest sections that were intermingled.

Change-Id: If0bbd6e182359c5186a8b958dd2c9ab9f0e0a3f3
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/17046
Tested-by: build bot (Jenkins)
Reviewed-by: Nico Huber <nico.h@gmx.de>
1 file changed