Add repos needed for Compulab iot-gate-imx8

The imx8 platforms won't build directly from mainline at this time. Add
a manifest for the trees that support the Compulab imx8mm platform. This
commit just adds the repos. It doesn't add support for building yet.

Signed-off-by: Grant Likely <grant.likely@arm.com>
Change-Id: Idb39c8d82ed209e32ac23039dd3991ed65a2a807