net: iosm: drop custom netdev(s) removing

Since the last commit, the WWAN core will remove all our network
interfaces for us at the time of the WWAN netdev ops unregistering.
Therefore, we can safely drop the custom code that cleans the list of
created netdevs. Anyway it no longer removes any netdev, since all
netdevs were removed earlier in the wwan_unregister_ops() call.

Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Reviewed-by: M Chetan Kumar <m.chetan.kumar@intel.com>
CC: M Chetan Kumar <m.chetan.kumar@intel.com>
CC: Intel Corporation <linuxwwan@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>