Add link to early discussion of WNDR4500

On the pages summarizing the WNDR4500 - with a Broadcom SoC and currently not supported - please add a link to an early discussion about porting. On the web pages:

I believe that that thread will be useful to anyone who might be interested in this device.

The new link would be in addition to the link:
Forum Topic URL:

The hwdata page itself says:
"For adding new dropdown values, Contact a LEDE wiki admin (tmomas)", so, the LEDE Project Forum here is "contact", as far as I know...

And, BTW, those "tow/hwdata" pages should be more easily discoverable from the LEDE/OpenWRT home page. They should show-up in a device search, or some such, even for "unsupported" devices.