Added code to check constant bus restrictions for VOP formats (only one SGPR value or literal-constant may be used by the instruction).
Note that the same checks are performed by SIInstrInfo::verifyInstruction (used by lowering code).
Added LIT tests.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296873 91177308-0d34-0410-b5e6-96231b3b80d8