fs: refactor promises version of lchown and lchmod

Check for platform support first to save a level of indentation.

PR-URL: #20551
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>

lib/internal/fs/promises.js

@@ -376,21 +376,19 @@ async function chmod(path, mode) {
 }
 
 async function lchmod(path, mode) {
-  if (O_SYMLINK !== undefined) {
-    const fd = await open(path,
-                          O_WRONLY | O_SYMLINK);
-    return fchmod(fd, mode).finally(fd.close.bind(fd));
-  }
-  throw new ERR_METHOD_NOT_IMPLEMENTED();
+  if (O_SYMLINK === undefined)
+    throw new ERR_METHOD_NOT_IMPLEMENTED();
+
+  const fd = await open(path, O_WRONLY | O_SYMLINK);
+  return fchmod(fd, mode).finally(fd.close.bind(fd));
 }
 
 async function lchown(path, uid, gid) {
-  if (O_SYMLINK !== undefined) {
-    const fd = await open(path,
-                          O_WRONLY | O_SYMLINK);
-    return fchown(fd, uid, gid).finally(fd.close.bind(fd));
-  }
-  throw new ERR_METHOD_NOT_IMPLEMENTED();
+  if (O_SYMLINK === undefined)
+    throw new ERR_METHOD_NOT_IMPLEMENTED();
+
+  const fd = await open(path, O_WRONLY | O_SYMLINK);
+  return fchown(fd, uid, gid).finally(fd.close.bind(fd));
 }
 
 async function fchown(handle, uid, gid) {