[llvm] [SPIR-V] Fix ldexp exponent splat for vectors wider than four elements (PR #225617)

[Farzon Lotfi via llvm-commits]

farzonl wrote:

The HLSL team has a execution suite exercising ldexp we are testing with a vector of size 5 and I am not seeing us hit an assert. The execution tests are actually passing. So Im curious what you are doing different?:
https://github.com/llvm/offload-test-suite/pull/1463/changes#diff-0174d309ee330ad175a1611435dac837f32247e0aa359c76cb438cd0e2114c3cR9-R11
```hlsl
Out.Store<vector<float, 5> >(0, 
                               ldexp(In0.Load<vector<float, 5> >(0),
                                     In1.Load<vector<float, 5> >(0)));
```

https://github.com/llvm/llvm-project/pull/225617