AMDGPU/SI: Fix input vcc operand for VOP2b instructions

Adds vcc to output string input for e32. Allows option
of using e64 encoding with assembler.

Also fixes these instructions not implicitly reading exec.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@247074 91177308-0d34-0410-b5e6-96231b3b80d8
6 files changed