[d3d11] Hold reference to DxvkInstance

Hack to keep the instance alive which owns the adapters. Should
fix #1240 for now, but we should fix this properly later on.

src/d3d11/d3d11_device.cpp

@@ -2464,6 +2464,7 @@ namespace dxvk {
           D3D_FEATURE_LEVEL   FeatureLevel,
           UINT                FeatureFlags)
   : m_dxgiAdapter   (pAdapter),
+    m_dxvkInstance  (pDxvkAdapter->instance()),
     m_dxvkAdapter   (pDxvkAdapter),
     m_dxvkDevice    (CreateDevice(FeatureLevel)),
     m_d3d11Device   (this, FeatureLevel, FeatureFlags),

src/d3d11/d3d11_device.h

@@ -641,6 +641,7 @@ namespace dxvk {
 
     Com<IDXGIAdapter>   m_dxgiAdapter;
 
+    Rc<DxvkInstance>    m_dxvkInstance;
     Rc<DxvkAdapter>     m_dxvkAdapter;
     Rc<DxvkDevice>      m_dxvkDevice;