[llvm] [RISCV] Use cached SubtargetInfo in AsmPrinter (NFC) (PR #147269)

[Petr Vesely via llvm-commits]

veselypeta wrote:

I don't have write access, so feel free to merge if everyone is happy. You can land it using my codasip email address. Thank you.

https://github.com/llvm/llvm-project/pull/147269