lantiq: xrx200_legacy: add alternative names for TP-Link TD-W9980(B)

lantiq: xrx200_legacy: add alternative names for TP-Link TD-W9980(B)

The TP-Link TD-W9980(B) shares the same hardware with the TP-Link TD-W8980.
The only difference is that the TD-W8980 does not support VDSL. This is a
software limitation and once the software is changed, both work equally
supporting VDSL. This commit adds alternative names for devices so they
can be easily found in the firmware selector.

Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
Link: https://github.com/openwrt/openwrt/pull/17583
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>