[llvm] [AMDGPU][SplitModule] Fix unintentional integer division (PR #117586)

[Pierre van Houtryve via llvm-commits]

================
@@ -15,19 +15,20 @@
 ; Also check w/o large kernels processing to verify they are indeed handled
 ; differently.
 
-; P0 is empty
----------------
Pierre-vh wrote:

The output of this test should not really change, try the change I suggested in SplitModule to see if it helps?

https://github.com/llvm/llvm-project/pull/117586