base-files: always generate default DUID
The previous logic was copied from 12_network-generate-ula, but fails to
account for upgrades where the "auto" value isn't set (it is set by
base-files/files/bin/config_generate). Fix this to always set the
default duid if it isn't set.
Also, rename the file to better reflect what it does.
Closes: #21029
Fixes: a660a076db5a ("base-files: generate a global DHCP DUID")
Link: https://github.com/openwrt/openwrt/pull/21118
Signed-off-by: David Härdeman <[email protected]>
Signed-off-by: Petr Štetiar <[email protected]> [fixes,closes tag]