We should never start a transmission after the queue has been stopped.

But because it might work we don't kill the function here but rather
warn loudly the user that something is wrong.

Set a flag when the queue should remain stopped. Reset this flag when
the queue actually gets restarded. Just check this value to know if a
transmission is legitimate, warn if it is not.

Turn the flags variable into an unsigned long to allow the use of atomic
helpers on it.
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/r/20220519150516.443078-11-miquel.raynal@bootlin.comSigned-off-by: Stefan Schmidt <stefan@datenfreihafen.org>