AMDGPU: Remove unnecessary reference (#162085)

Author: arsenm

llvm/lib/Target/AMDGPU/GCNSubtarget.cpp

@@ -541,7 +541,7 @@ unsigned GCNSubtarget::getMaxNumSGPRs(const Function &F) const {
 
 unsigned GCNSubtarget::getBaseMaxNumVGPRs(
     const Function &F, std::pair<unsigned, unsigned> NumVGPRBounds) const {
-  const auto &[Min, Max] = NumVGPRBounds;
+  const auto [Min, Max] = NumVGPRBounds;
 
   // Check if maximum number of VGPRs was explicitly requested using
   // "amdgpu-num-vgpr" attribute.