[llvm] [RISCV] Add initial assembler/MC layer support for big-endian (PR #146534)

[Djordje Todorovic via llvm-commits]

djtodoro wrote:

> See the thread starting at [riscv-non-isa/riscv-elf-psabi-doc#265 (comment)](https://github.com/riscv-non-isa/riscv-elf-psabi-doc/issues/265#issuecomment-2148592299)

Thanks a lot for providing this! I guess these problems should be addressed within https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/470.

https://github.com/llvm/llvm-project/pull/146534