wifi-scripts: add missing 'network' property to wifi-iface schema

wifi-scripts: add missing 'network' property to wifi-iface schema

The ucode-based wifi interface validation is based on `hostapd.conf`
specific options, which means it's missing the OpenWrt-specific
'network' property.

This causes schema validation warnings like:
```
daemon.notice netifd: radio1 (1340): wifi-scripts: network is not present in the schema
```

The description is taken from the OpenWrt wiki:
https://openwrt.org/docs/guide-user/network/wifi/basic#common_options1

Signed-off-by: Sean Khan <datapronix@protonmail.com>
Link: https://github.com/openwrt/openwrt/pull/18946
Signed-off-by: Robert Marko <robimarko@gmail.com>