cmd/link: do not align type name data

Now that reflect.name objects contain an offset to pkgPath instead of a
pointer, there is no need to align the symbol data.

Removes approx. 10KB from the cmd/go binary. The effect becomes more
important later as more type data is moved into name objects.

For #6853

Change-Id: Idb507fdbdad04f16fc224378f82272cb5c236ab7
Reviewed-on: https://go-review.googlesource.com/21776
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/link/internal/ld/data.go

@@ -1116,7 +1116,7 @@ func symalign(s *LSym) int32 {
 	} else if s.Align != 0 {
 		return min
 	}
-	if strings.HasPrefix(s.Name, "go.string.") && !strings.HasPrefix(s.Name, "go.string.hdr.") {
+	if (strings.HasPrefix(s.Name, "go.string.") && !strings.HasPrefix(s.Name, "go.string.hdr.")) || strings.HasPrefix(s.Name, "type..namedata.") {
 		// String data is just bytes.
 		// If we align it, we waste a lot of space to padding.
 		return min