cmd/compile: fix error message on loong64

Change-Id: I90428330b17ab9f93ae94a77cefc24464e225df5
Reviewed-on: https://go-review.googlesource.com/c/go/+/717700
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Meidan Li <limeidan@loongson.cn>
Reviewed-by: sophie zhao <zhaoxiaolin@loongson.cn>
Reviewed-by: Michael Knyszek <mknyszek@google.com>

Author: abner-chenc

src/cmd/compile/internal/loong64/ssa.go

@@ -692,7 +692,7 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 			//   vs
 			//     16 instructions in the straightline code
 			//   Might as well use straightline code.
-			v.Fatalf("ZeroLoop size too small %d", n)
+			v.Fatalf("MoveLoop size too small %d", n)
 		}
 
 		// Put iteration count in a register.