[llvm] [RISCV] Enable load clustering by default (PR #73789)

[Pengcheng Wang via llvm-commits]

https://github.com/wangpc-pp approved this pull request.

LGTM! Thanks a lot!
We have already enabled it internally, and we do see some improvements on LMBench.

https://github.com/llvm/llvm-project/pull/73789