go.tools/ssa: s/Ret/Return/g

R=gri
CC=golang-dev
https://golang.org/cl/14526044
diff --git a/pointer/gen.go b/pointer/gen.go
index b4c19e2..154cde6 100644
--- a/pointer/gen.go
+++ b/pointer/gen.go
@@ -989,7 +989,7 @@
 			}
 		}
 
-	case *ssa.Ret:
+	case *ssa.Return:
 		results := a.funcResults(cgn.obj)
 		for _, r := range instr.Results {
 			sz := a.sizeof(r.Type())