cmd/compile: eliminate unused Sig.offset field

Change-Id: If498d1fc6e8c0c4e8cf7ed38c4997adf05e003a6
Reviewed-on: https://go-review.googlesource.com/105043
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dave Cheney <dave@cheney.net>

src/cmd/compile/internal/gc/reflect.go

@@ -48,7 +48,6 @@ type Sig struct {
 	tsym  *types.Sym
 	type_ *types.Type
 	mtype *types.Type
-	offset int32
 }
 
 // siglt sorts method signatures by name with exported methods first,
@@ -473,7 +472,6 @@ func imethods(t *types.Type) []*Sig {
 		}
 
 		sig.mtype = f.Type
-		sig.offset = 0
 		sig.type_ = methodfunc(f.Type, nil)
 
 		if n := len(methods); n > 0 {