go/ssa: slight simplification to setCallFunc
go/ssa: slight simplification to setCallFunc

Change-Id: I6b8cc35f779910ebab3db9994bb17456a6df4b94
Reviewed-on: https://go-review.googlesource.com/2742
Reviewed-by: Robert Griesemer <a6752097faebf1f02d80107d77a9be009089afe3@golang.org>

runcom/tools,maddyonline/tools,syreclabs/go-tools,sshetty10/tools,4ad/tools,syreclabs/go-tools,golang/tools,nicot/tools,jdhenke/tools,golang/tools,matryer/tools,magiccao/tools,springning/tools,josharian/tools,argandas/tools,syreclabs/go-tools,cw2018/tools,runcom/tools,cmars/tools,matryer/tools,sshetty10/tools,cmars/tools,maddyonline/tools,syreclabs/go-tools,glasser/golang-tools,magiccao/tools,cmars/tools,4ad/tools,springning/tools,dmitris/tools,sshetty10/tools,glasser/golang-tools,4ad/tools,cmars/tools,argandas/tools,dmitris/tools,magiccao/tools,sshetty10/tools,josharian/tools,springning/tools,jdhenke/tools,golang/tools,glasser/golang-tools,golang/tools,jdhenke/tools,nicot/tools,runcom/tools,nicot/tools,cw2018/tools,matryer/tools,jdhenke/tools,maddyonline/tools,cw2018/tools,syreclabs/go-tools,dmitris/tools,josharian/tools,cw2018/tools,nicot/tools,matryer/tools,argandas/tools,maddyonline/tools,runcom/tools,golang/tools,argandas/tools,magiccao/tools,springning/tools,dmitris/tools,glasser/golang-tools,syreclabs/go-tools,josharian/tools