[clang] [flang] [llvm] [RISCV] Make "target-feature +i" explicit (PR #157835)

[Sam Elliott via llvm-commits]

https://github.com/lenary approved this pull request.

LGTM. This will be good as cheri stuff starts appearing, which has a different base architecture.

https://github.com/llvm/llvm-project/pull/157835