Add two KUnit test cases for the drm_framebuffer_lookup function, one for the base case, that tests if the lookup finds the correct framebuffer object and another that tests the lookup for an inexistent framebuffer. Signed-off-by: Carlos Eduardo Gallo Filho <gcarlos@disroot.org> Acked-by: Maxime Ripard <mripard@kernel.org> Link: https://patchwork.freedesktop.org/patch/msgid/20240911001559.28284-8-gcarlos@disroot.org Signed-off-by: Maxime Ripard <mripard@kernel.org>