configs/kontron_smarc_sal28: enable u-boot

Enable building of the bootloader and integrate it into the resulting
image.

Signed-off-by: Michael Walle <michael@walle.cc>
Tested-by: Heiko Thiery <heiko.thiery@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
3 files changed