net/mlx5: panic when destroying a queue in use

Since the queue release API does not allow failures (return value is void)
and the flow API does not allow a queue to be released as long as a flow
rule depends on it, the only rational decision to avoid undefined behavior
is to panic in this situation.

Signed-off-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>
Acked-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>