[flang] Fix PPC and AARCH64 after #73301 (#74591)

After https://github.com/llvm/llvm-project/pull/73301, all semantics
tests using `triple XXX` options need to have a
`REQUIRED: XX-registered-target` since the llvm::TargetMachine is needed
to get the llvm::DataLayout before semantics.

Fix three tests that lacked this.

Fixes:
https://lab.llvm.org/buildbot/#/builders/21/builds/87263
https://lab.llvm.org/buildbot/#/builders/268/builds/3841