[libunwind] [AMDGPU] Add another SIFoldOperands instance after shrink (PR #67878)

[Stanislav Mekhanoshin via cfe-commits]

rampitec wrote:

I have measured compile time performance impact with timing check-llvm-codegen-amdgpu on the release build:

```
before the patch:           11.06s
add folding:                11.09s +0.2%
remove folding from shrink: 11.02s -0.4%
```
In general the impact smaller than run to run variance, the numbers are median time of 5 runs.

https://github.com/llvm/llvm-project/pull/67878