[RISCV] Support overloaded version ntlh intrinsic function

Here is the proposal https://github.com/riscv-non-isa/riscv-c-api-doc/pull/47.

The version that omit the domain argument imply domain=__RISCV_NTLH_ALL.

```
type __riscv_ntl_load (type *ptr);
void __riscv_ntl_store (type *ptr, type val);
```

Reviewed By: kito-cheng, craig.topper

Differential Revision: https://reviews.llvm.org/D156221