vl: Use error_fatal to simplify obvious fatal errors (again)

vl: Use error_fatal to simplify obvious fatal errors (again)

Patch created mechanically by rerunning:

    $ spatch --in-place --sp-file scripts/coccinelle/use-error_fatal.cocci \
             --macro-file scripts/cocci-macro-file.h vl.c

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20181213175807.12039-1-armbru@redhat.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>