cmd/...: remove use of func() { ... }() in loop increment

These were introduced during C -> Go translation when the loop increment
contained multiple statements.

Change-Id: Ic8abd8dcb3308851a1f7024de00711f0f984e684
Reviewed-on: https://go-review.googlesource.com/7627
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Rob Pike <r@golang.org>

src/cmd/internal/ld/data.go

@@ -1032,7 +1032,7 @@ func proggenarray(g *ProgGen, length int64) {
 
 	proggendataflush(g)
 	proggenemit(g, obj.InsArray)
-	for i = 0; i < int32(Thearch.Ptrsize); (func() { i++; length >>= 8 })() {
+	for i = 0; i < int32(Thearch.Ptrsize); i, length = i+1, length>>8 {
 		proggenemit(g, uint8(length))
 	}
 }