[clang] [Clang] Remove 3-element vector load and store special handling (PR #104661)

[Shilei Tian via cfe-commits]

================
@@ -45,7 +45,7 @@ void test3(packedfloat3 *p) {
   *p = (packedfloat3) { 3.2f, 2.3f, 0.1f };
 }
 // CHECK: @test3(
-// CHECK: store <4 x float> {{.*}}, align 4
+// CHECK: store <3 x float> {{.*}}, align 4
----------------
shiltian wrote:

Eventually we might do it like:

```
bool preserveVec3(Triple TT, bool IsHLSL) {
  if (IsHLSL)
    return true;
  if (TT.isAMDGPU())
    return true;
  return false;
}
```

https://github.com/llvm/llvm-project/pull/104661