CDFS driver shoudn't use RtlIsNameLegalDOS8Dot3

RtlIsNameLegalDOS8Dot3 -> RtlUpcaseUnicodeStringToCountedOemString -> RtlUpcaseUnicodeToOemN

RtlUpcaseUnicodeToOemN requires table NlsUnicodeToOemTable

but as soon as CD booting , the CDFS call RtlIsNameLegalDOS8Dot3,
and that time NLS not even loaded, so NlsUnicodeToOemTable is NULL