[SPIR-V] Assert reached when splatting a vector to a scalar inout param

Follow up from #6747 :

void bar (inout float p) { }

[numthreads(1, 1, 1)]
void main() {
    int3 a = 0;
    bar(a);
}

dxc -T cs_6_6 -E main -spirv -fcgl repro.hlsl
dxc: /home/nathan/projects/mainline/DirectXShaderCompiler/tools/clang/lib/SPIRV/SpirvEmitter.cpp:1364: clang::spirv::SpirvInstruction* clang::spirv::SpirvEmitter::castToType(clang::spirv::SpirvInstruction*, clang::QualType, clang::QualType, clang::SourceLocation, clang::SourceRange): Assertion `isVectorType(fromType, nullptr, &fromSize) == isVectorType(toType, nullptr, &toSize) && fromSize == toSize' failed.
Aborted (core dumped)

Passing a float to a inout float3 function parameter is allowed and only the first float. But seems like if a float3 is passed to a function only taking a inout float, it should be an error.