curl_endian: Fixed build when 64-bit integers are not supported (Part 2)

Missed Curl_read64_be() in commit bb12d44471 :(

lib/curl_endian.c

@@ -138,6 +138,7 @@ unsigned int Curl_read32_be(unsigned char *buf)
          ((unsigned int)buf[2] << 8) | ((unsigned int)buf[3]);
 }
 
+#if (CURL_SIZEOF_CURL_OFF_T > 4)
 /*
  * Curl_read64_be()
  *
@@ -173,6 +174,8 @@ unsigned __int64 Curl_read64_be(unsigned char *buf)
 }
 #endif
 
+#endif /* CURL_SIZEOF_CURL_OFF_T > 4 */
+
 /*
  * Curl_write16_le()
  *