locale.c: Avoid unnecessary work around localeconv()

There are now two different functions that return the values for
localeconv().  One is for when the locale is "C"; the other for
everything else.  The C one returns values that don't need adjusting, so
skip that for this case.

locale.c

@@ -5724,23 +5724,29 @@ S_my_localeconv(pTHX_ const int item)
 
     for (unsigned int i = 0; i < 2; i++) {  /* Try both types of strings */
 
+        /* The return from this function is already adjusted */
+        if (populate[i] == S_populate_hash_from_C_localeconv) {
+            continue;
+        }
+
         /* Examine each string */
         for (const lconv_offset_t *strp = strings[i]; strp->name; strp++) {
             const char * name = strp->name;
 
             /* 'value' will contain the string that may need to be marked as
              * UTF-8 */
             SV ** value = hv_fetch(hv, name, strlen(name), true);
-            if (! value || ! SvPOK(*value)) {
+            if (value == NULL) {
                 continue;
             }
 
             /* Determine if the string should be marked as UTF-8. */
-            if (UTF8NESS_YES == (get_locale_string_utf8ness_i(SvPVX(*value),
-                                                  LOCALE_UTF8NESS_UNKNOWN,
-                                                  locales[i],
-                                                  LC_ALL_INDEX_ /* OOB */)))
-            {
+            if (   UTF8NESS_YES
+                == (get_locale_string_utf8ness_i(SvPVX(*value),
+                                                 LOCALE_UTF8NESS_UNKNOWN,
+                                                 locales[i],
+                                                 LC_ALL_INDEX_ /* OOBounds */
+            ))) {
                 SvUTF8_on(*value);
             }
         }