net: devres: rename the release callback of devm_register_netdev()

Make it an explicit counterpart to devm_register_netdev() just like we
do with devm_free_netdev() for better clarity.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>