[llvm] [RISCV] Mark symbols used in inline asm for relocations as referenced (PR #104925)

[Pengcheng Wang via llvm-commits]

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

LGTM. Thanks!
(Actually, this is a problem I have already found when I was implementing [it](https://reviews.llvm.org/D158062), but I didn't put it in mind).

https://github.com/llvm/llvm-project/pull/104925