[flang] Support "PRINT NML"

[klausler]

It's not conforming, but 6 out of 7 compilers tested support the use of a namelist name as the format in a PRINT statement with no data-list.

[klausler]

#112024

[llvmbot]

@llvm/issue-subscribers-flang-frontend

Author: Peter Klausler (klausler)

It's not conforming, but 6 out of 7 compilers tested support the use of a namelist name as the format in a PRINT statement with no data-list.