scripts: add_namespace: Fix coccicheck failed

Now all scripts in scripts/coccinelle to be automatically called
by coccicheck. However new adding add_namespace.cocci does not
support report mode, which make coccicheck failed.
This add "virtual report" to  make the coccicheck go ahead smoothly.

Fixes: eb8305ae ("scripts: Coccinelle script for namespace dependencies.")
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
Acked-by: Matthias Maennich <maennich@google.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Jessica Yu <jeyu@kernel.org>