[AMDGPU] Don't combine DPP if DPP register is used more than once per instruction

Reviewers: arsenm, rampitec, foad

Reviewed By: rampitec, foad

Subscribers: wuzish, kzhuravl, nemanjai, jvesely, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, hiraditya, kbarton, kerbowa, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D82551