[AMDGPU] Remove getMaxWavesPerCU in favour of getWavesPerWorkGroup.

[foad]

Summary

These methods were identical. I chose to remove getMaxWavesPerCU because
I think Max in the name was misleading. NFC.

llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.h

 /// STI.
 unsigned getEUsPerCU(const MCSubtargetInfo *STI);
 
 /// \returns Maximum number of work groups per compute unit for given subtarget
 /// \p STI and limited by given \p FlatWorkGroupSize.
 unsigned getMaxWorkGroupsPerCU(const MCSubtargetInfo *STI,
                                unsigned FlatWorkGroupSize);
 
-/// \returns Maximum number of waves per compute unit for given subtarget \p
-/// STI and limited by given \p FlatWorkGroupSize.
-unsigned getMaxWavesPerCU(const MCSubtargetInfo *STI,
-                          unsigned FlatWorkGroupSize);
-
 /// \returns Minimum number of waves per execution unit for given subtarget \p
 /// STI.
 unsigned getMinWavesPerEU(const MCSubtargetInfo *STI);
 
 /// \returns Maximum number of waves per execution unit for given subtarget \p
 /// STI without any kind of limitation.
 unsigned getMaxWavesPerEU(const MCSubtargetInfo *STI);
 

llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp

if (STI->getTargetTriple().getArch() != Triple::amdgcn)
     return 8;
   unsigned N = getWavesPerWorkGroup(STI, FlatWorkGroupSize);
   if (N == 1)
     return 40;
   N = 40 / N;
   return std::min(N, 16u);
 }
 
-unsigned getMaxWavesPerCU(const MCSubtargetInfo *STI,
-                          unsigned FlatWorkGroupSize) {
-  return getWavesPerWorkGroup(STI, FlatWorkGroupSize);
-}
-
 unsigned getMinWavesPerEU(const MCSubtargetInfo *STI) {
   return 1;
 }
 
 unsigned getMaxWavesPerEU(const MCSubtargetInfo *STI) {
   // FIXME: Need to take scratch memory into account.
   if (!isGFX10(*STI))
     return 10;
   return 20;
 }
 
 unsigned getMaxWavesPerEU(const MCSubtargetInfo *STI,
                           unsigned FlatWorkGroupSize) {
-  return divideCeil(getMaxWavesPerCU(STI, FlatWorkGroupSize), getEUsPerCU(STI));
+  return divideCeil(getWavesPerWorkGroup(STI, FlatWorkGroupSize),
+                    getEUsPerCU(STI));
 }
 
 unsigned getMinFlatWorkGroupSize(const MCSubtargetInfo *STI) {
   return 1;
 }
 
 unsigned getMaxFlatWorkGroupSize(const MCSubtargetInfo *STI) {
   // Some subtargets allow encoding 2048, but this isn't tested or supported.