runtime: use uint32 arrays in BenchmarkClearFat*

The CopyFat benchmarks were changed in CL 92760044. See CL 111350043 for discussion.

LGTM=khr
R=khr
CC=golang-codereviews
https://golang.org/cl/116000043

src/pkg/runtime/memmove_test.go

@@ -164,49 +164,49 @@ func BenchmarkMemclr65536(b *testing.B) { bmMemclr(b, 65536) }
 
 func BenchmarkClearFat16(b *testing.B) {
 	for i := 0; i < b.N; i++ {
-		var x [16]byte
+		var x [16 / 4]uint32
 		_ = x
 	}
 }
 func BenchmarkClearFat24(b *testing.B) {
 	for i := 0; i < b.N; i++ {
-		var x [24]byte
+		var x [24 / 4]uint32
 		_ = x
 	}
 }
 func BenchmarkClearFat32(b *testing.B) {
 	for i := 0; i < b.N; i++ {
-		var x [32]byte
+		var x [32 / 4]uint32
 		_ = x
 	}
 }
 func BenchmarkClearFat64(b *testing.B) {
 	for i := 0; i < b.N; i++ {
-		var x [64]byte
+		var x [64 / 4]uint32
 		_ = x
 	}
 }
 func BenchmarkClearFat128(b *testing.B) {
 	for i := 0; i < b.N; i++ {
-		var x [128]byte
+		var x [128 / 4]uint32
 		_ = x
 	}
 }
 func BenchmarkClearFat256(b *testing.B) {
 	for i := 0; i < b.N; i++ {
-		var x [256]byte
+		var x [256 / 4]uint32
 		_ = x
 	}
 }
 func BenchmarkClearFat512(b *testing.B) {
 	for i := 0; i < b.N; i++ {
-		var x [512]byte
+		var x [512 / 4]uint32
 		_ = x
 	}
 }
 func BenchmarkClearFat1024(b *testing.B) {
 	for i := 0; i < b.N; i++ {
-		var x [1024]byte
+		var x [1024 / 4]uint32
 		_ = x
 	}
 }