R600/SI: cleanup literal handling v3

Seems to be allot simpler, and also paves the
way for further improvements.

v2: rebased on master, use 0 in BUFFER_LOAD_FORMAT_XYZW,
    use VGPR0 in dummy EXP, avoid compiler warning, break
    after encoding the first literal.
v3: correctly use V_ADD_F32_e64

This is a candidate for the stable branch.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Tom Stellard <thomas.stellard@amd.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175354 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/R600/AMDGPUTargetMachine.cpp

@@ -145,7 +145,6 @@ bool AMDGPUPassConfig::addPreEmitPass() {
     addPass(&FinalizeMachineBundlesID);
     addPass(createR600LowerConstCopy(*TM));
   } else {
-    addPass(createSILowerLiteralConstantsPass(*TM));
     addPass(createSILowerControlFlowPass(*TM));
   }