[AMDGPU] link dpp pseudos and real instructions on gfx10

[AMDGPU] link dpp pseudos and real instructions on gfx10

This defaults to zero fi operand, but we do not expose it
anyway. Should we expose it later it needs to be added to
the pseudo.

This enables dpp combining on gfx10.

Differential Revision: https://reviews.llvm.org/D68888

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@374604 91177308-0d34-0410-b5e6-96231b3b80d8