cmd/compile/internal/ssa: remove unused PrintFunc variable

Change-Id: I8c581eec77beacaddc0aac29e7d380a4d5ca8acc
Reviewed-on: https://go-review.googlesource.com/37551
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/compile/internal/ssa/export_test.go

@@ -13,7 +13,6 @@ import (
 )
 
 var CheckFunc = checkFunc
-var PrintFunc = printFunc
 var Opt = opt
 var Deadcode = deadcode
 var Copyelim = copyelim