The Up squared 6000 use an IGB based card so enable it in the
configuration

Signed-off-by: Sjoerd Simons <sjoerd@collabora.com>

gitlab-ci: Enable debug uart config options for UP Squared 6000 board

See merge request !1

This commit adds the EXTRACONFIG parameter to the target platform
configurations in the gitlab CI. The config options in this parameter
will be enabled on top of the selected defconfig.

In particular, this enables the required config options to have debug
UART enabled on x64 UP Squared 6000 boards.

Signed-off-by: Ariel D'Alessandro <ariel.dalessandro@collabora.com>