cmd/compile: use NumElem instead of Type.Bound

This eliminates all direct reads of Type.Bound
outside type.go.

Change-Id: I0a9a72539f8f4c0de7f5e05e1821936bf7db5eb7
Reviewed-on: https://go-review.googlesource.com/21421
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/src/cmd/compile/internal/gc/gen.go b/src/cmd/compile/internal/gc/gen.go
index 1de63ae..f99e8d4 100644
--- a/src/cmd/compile/internal/gc/gen.go
+++ b/src/cmd/compile/internal/gc/gen.go
@@ -1215,7 +1215,7 @@
 			return true
 		}
 
-		for i := int64(0); i < t.Bound; i++ {
+		for i := int64(0); i < t.NumElem(); i++ {
 			if !visitComponents(t.Elem(), startOffset+i*t.Elem().Width, f) {
 				return false
 			}