[clang] [clang][RISCV] Extend intrinsic size check variable from 16 -> 32 bits. NFC (PR #111481)

[Jerry Zhang Jian via cfe-commits]

jerryzj wrote:

> Why doesn't any test catch it?

I suppose the [CI](https://github.com/riscv-non-isa/rvv-intrinsic-doc/actions/runs/11216383892/job/31175562939) of intrinsic doc should catch this, but it is not reporting errors as expected.
I happen to notice the failures and working on a fix now.

https://github.com/llvm/llvm-project/pull/111481