Revert "[15/15][Clang][RISCV][NFC] Set data member under Policy as constants"

This reverts commit 2b807336.

This change is causing Windows builds to hang and out of memory errors with clang-15:
 - https://lab.llvm.org/buildbot/#/builders/17/builds/33129
 - https://lab.llvm.org/buildbot/#/builders/174/builds/17069
 - https://lab.llvm.org/buildbot/#/builders/83/builds/28484
 - https://lab.llvm.org/buildbot/#/builders/172/builds/22803
 - https://lab.llvm.org/buildbot/#/builders/216/builds/16210