Fix MSVC warning - "'llvm::AMDGPUResourceUsageAnalysis': type name first seen using 'class' now seen using 'struct'". NFC.

llvm/lib/Target/AMDGPU/AMDGPUAsmPrinter.h

diff --git a/llvm/lib/Target/AMDGPU/AMDGPUAsmPrinter.h b/llvm/lib/Target/AMDGPU/AMDGPUAsmPrinter.h
index df7a499..63589d2 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUAsmPrinter.h
+++ b/llvm/lib/Target/AMDGPU/AMDGPUAsmPrinter.h
@@ -21,7 +21,7 @@
 namespace llvm {
 
 class AMDGPUMachineFunction;
-struct AMDGPUResourceUsageAnalysis;
+class AMDGPUResourceUsageAnalysis;
 class AMDGPUTargetStreamer;
 class MCCodeEmitter;
 class MCOperand;