[clang] [llvm] [RISCV] Add Spacemit X100 processor definition (PR #173988)

[Mark Zhuang via cfe-commits]

zqb-all wrote:

GitHub indicates that this patch has conflicts. After clicking the button to resolve the conflicts, it shows as "Merge branch 'main' into spacemit-x100". If I have made a mistake or if there is anything else I need to do to meet the requirements for patch merging, please let me know. Thanks :)

https://github.com/llvm/llvm-project/pull/173988