OpenWrt Chaos Calmer 15.05.1 branch ipq

Where can i find this branch?

No longer supported.

Your post does not appear to be related to an officially released OpenWrt version, package or supported operation.

It is unlikely that you will receive useful input here.

Please seek advise from the relevant maintainer.

It never existed in the first place, ipq806x support premiered with 17.01.0.