device: add support for configuring devices with external auth handler

device: add support for configuring devices with external auth handler

This can be used to support 802.1x on wired devices.
In order to use this, the device section for each port needing authentication
needs to contain the option auth 1
When set, this option prevents devices from being added to bridges or configured
with IP settings by default, until the set_state ubus call on network.device
sets "auth_status" to true for the device.

Signed-off-by: Felix Fietkau <nbd@nbd.name>