ipv6: simplify init function for freebsd
ipv6: simplify init function for freebsd

Change-Id: I515bdaf3f30b00d61c341295e549bb4c2163bd54
Reviewed-on: https://go-review.googlesource.com/11293
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

veliamsli/net,subuk/net,cmars/tools,subuk/net,cesanta/goxnet,gomini/net,w4ngyi/net,albertjin/golang-net,DramaFever/golang.org-x-net,cmars/tools,gomini/net,zabawaba99/net,golang/net,kiip/net,mckinney-subgraph/net,dafyddcrosby/net,raboof/net,dafyddcrosby/net,DramaFever/golang.org-x-net,cmars/tools,albertjin/golang-net,w4ngyi/net,yangxianjun/net,zabawaba99/net,flowlo/go-net,veliamsli/net,muzining/net,yangxianjun/net,cesanta/goxnet,mckinney-subgraph/net,kiip/net,muzining/net,cmars/tools,raboof/net,flowlo/go-net