[NOUPSTREAM] Add GitLab CI support

Add CI support. This will do the following:

1. Run dt_binding_check to make sure no major flaws were introduced in
   the DT bindings
2. Run dtbs_check, for Rock 5A, Rock 5B and EVB1. If warnings are
   generated the CI will report that as warning
3. Build a Kernel .deb package
4. Generate a test job for LAVA and run it

Co-developed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Co-developed-by: Sjoerd Simons <sjoerd@collabora.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Sjoerd Simons <sjoerd@collabora.com>
Signed-off-by: Christopher Obbard <chris.obbard@collabora.com>