[RISCV] Refine pre-define macro tests

1. Undefined macro test for rv32i and rv64i.
  a. Reorder it with canonical order.
  b. Add missing  undefined macro check.
  c. Append defined value to `__riscv_a`, `__riscv_f` and `__riscv_c` to distinguish with
      `__riscv_arch_test`, `__riscv_cmodel_medlow` and `__riscv_float_abi_soft`. They have the same prefix.
2. Move abi macro test below f and d.
3. Unify coding style for newline.

Reviewed By: HsiangKai

Differential Revision: https://reviews.llvm.org/D99631