net: wwan: iosm: Remove DEBUG flag

Author forgot to remove that flag.

Fixes: f7af616c ("net: iosm: infrastructure")
Reported-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>