crypto: remove obsolete encoding check

This renames the parameters for clarity and removes the check for
undefined encoding. That will always default to `utf8`.

PR-URL: #26809
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/internal/crypto/util.js

@@ -55,13 +55,13 @@ function getDefaultEncoding() {
 // This is here because many functions accepted binary strings without
 // any explicit encoding in older versions of node, and we don't want
 // to break them unnecessarily.
-function toBuf(str, encoding) {
-  if (typeof str === 'string') {
-    if (encoding === 'buffer' || !encoding)
+function toBuf(val, encoding) {
+  if (typeof val === 'string') {
+    if (encoding === 'buffer')
       encoding = 'utf8';
-    return Buffer.from(str, encoding);
+    return Buffer.from(val, encoding);
   }
-  return str;
+  return val;
 }
 
 const getCiphers = cachedResult(() => filterDuplicateStrings(_getCiphers()));