[clang] [CIR] Add poison attribute (PR #150760)

[Henrich Lauko via cfe-commits]

================
@@ -127,7 +127,7 @@ def CIR_BoolAttr : CIR_Attr<"Bool", "bool", [TypedAttrInterface]> {
 // ZeroAttr
 //===----------------------------------------------------------------------===//
 
-def ZeroAttr : CIR_TypedAttr<"Zero", "zero"> {
+def CIR_ZeroAttr : CIR_TypedAttr<"Zero", "zero"> {
----------------
xlauko wrote:

This is being upstreamed in parallel PR https://github.com/llvm/llvm-project/pull/150694 and is related to poison. Please roll back:

```suggestion
def ZeroAttr : CIR_TypedAttr<"Zero", "zero"> {
```

https://github.com/llvm/llvm-project/pull/150760