[llvm] [TwoAddressInstruction] Check if segment was found when updating subreg LIs (PR #65916)

[Luke Lau via llvm-commits]

lukel97 wrote:

@BeMg Thanks for running that, I think they should be the same. The only subrange in `%1` should be `sub_vrm1_0` right? I believe that's the lane mask L0000000000000004. Looks the subrange L00000000000003C0 should be removed in this test case. Will take a look

https://github.com/llvm/llvm-project/pull/65916