[RISCV] Update the canonical extension order

LLVM embeds the order of one-letter standard extensions in . The order in the specification was updated by from `IMAFDQLCBKJTPVH` to ~`IMAFDQLCBJTVPKH`~ `IMAFDQLCBKJTVPH` (P moved after V). The code needs to be updated accordingly.

Open llvm/include/llvm/Support/RISCVISAUtils.h at the canonical extension order near line 24. Compare the embedded order with the specification change described in the issue, update it to IM AFDQLCBKJTVPH without spaces, and verify that the header reflects the requested canonical order.

Written by the indexing model from the issue text.