Fix the problem that duplicate type names exist in OPEN TYPE.

The following excerpt of ASN.1 of X2AP is one example.

  HandoverRequestAcknowledge-IEs X2AP-PROTOCOL-IES ::= {
    { ID id-Old-eNB-UE-X2AP-ID  CRITICALITY ignore  TYPE UE-X2AP-ID  PRESENCE mandatory}|
    { ID id-New-eNB-UE-X2AP-ID  CRITICALITY ignore  TYPE UE-X2AP-ID  PRESENCE mandatory}|
    ...
  }