SILoadStoreOptimizer.cpp: Fix build; Clang doesn't like "using anonymous struct" since rL315256.

llvm-svn: 315283
diff --git a/llvm/lib/Target/AMDGPU/SILoadStoreOptimizer.cpp b/llvm/lib/Target/AMDGPU/SILoadStoreOptimizer.cpp
index 8b3fdd8..026fd97 100644
--- a/llvm/lib/Target/AMDGPU/SILoadStoreOptimizer.cpp
+++ b/llvm/lib/Target/AMDGPU/SILoadStoreOptimizer.cpp
@@ -69,7 +69,7 @@
 namespace {
 
 class SILoadStoreOptimizer : public MachineFunctionPass {
-  using CombineInfo = struct {
+  struct CombineInfo {
     MachineBasicBlock::iterator I;
     MachineBasicBlock::iterator Paired;
     unsigned EltSize;