[AMDGPU] Fix an issue in `op_sel_hi` skipping.

[AMDGPU] Fix an issue in `op_sel_hi` skipping.

Summary:
- Only apply packed literal `op_sel_hi` skipping on operands requiring
  packed literals. Even an instruction is `packed`, it may have operand
  requiring non-packed literal, such as `v_dot2_f32_f16`.

Reviewers: rampitec, arsenm, kzhuravl

Subscribers: jvesely, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60978

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@358922 91177308-0d34-0410-b5e6-96231b3b80d8