[llvm] [CodeGen] Provide original IR type to CC lowering (NFC) (PR #152709)

[Daniel Thornburgh via llvm-commits]

mysterymath wrote:

Hey, we're seeing Fuchsia Rust toolchain build failures due to this:
https://logs.chromium.org/logs/fuchsia/buildbucket/cr-buildbucket/8706814125736858065/+/u/rust_install/stdout?format=raw

```
lib/Target/Xtensa/CMakeFiles/LLVMXtensaCodeGen.dir/XtensaISelLowering.cpp.o -c /b/s/w/ir/x/w/fuchsia-third_party-rust/src/llvm-project/llvm/lib/Target/Xtensa/XtensaISelLowering.cpp
/b/s/w/ir/x/w/fuchsia-third_party-rust/src/llvm-project/llvm/lib/Target/Xtensa/XtensaISelLowering.cpp:439:10: error: cannot initialize return object of type 'CCAssignFn *' (aka 'bool (*)(unsigned int, MVT, MVT, CCValAssign::LocInfo, ISD::ArgFlagsTy, Type *, CCState &)') with an lvalue of type 'bool (unsigned int, MVT, MVT, CCValAssign::LocInfo, ISD::ArgFlagsTy, CCState &)': different number of parameters (7 vs 6)
  439 |   return CC_Xtensa_Custom;
      |          ^~~~~~~~~~~~~~~~
1 error generated.
[2507/3092] Building CXX
```

I'm new to oncall our Rust toolchain, but others recommended that I ping here, since this may affect other Rust builds too. Would you have the time to fix the XTensa header too?

https://github.com/llvm/llvm-project/pull/152709