GPU: Fix D3D12 tearing query

src/gpu/d3d12/SDL_gpu_d3d12.c

@@ -733,7 +733,7 @@ struct D3D12Renderer
     SDL_SharedObject *dxgidebug_dll;
 #endif
     ID3D12Debug *d3d12Debug;
-    bool supportsTearing;
+    BOOL supportsTearing;
     SDL_SharedObject *d3d12_dll;
     ID3D12Device *device;
     PFN_D3D12_SERIALIZE_ROOT_SIGNATURE D3D12SerializeRootSignature_func;