[llvm] Add live in for PrivateSegmentSize in GISel path (PR #139968)

[Matt Arsenault via llvm-commits]

================
@@ -0,0 +1,22 @@
+; NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 5
+; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx1300 -global-isel -stop-after=prologepilog -o - %s | FileCheck %s
----------------
arsenm wrote:

Better 
```suggestion
; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx1200 -global-isel -stop-after=prologepilog -o - %s | FileCheck %s
```

https://github.com/llvm/llvm-project/pull/139968