payloads/external: Download iPXE over HTTPS

Change-Id: Ie4979ab8491ee821b39a273c5f354c445105d2a4
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-on: https://review.coreboot.org/17971
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
1 file changed