[d3d11] Do not flush on every call to GetData

There are several scenarios when flushing can have
a significant negative impact on performance:
1. When the query result is already available
2. When the game scatters GetData calls when rendering

Frostpunk hits both issues at the same time, which led to
over 120 queue submissions per frame. This patch reduces
that to 3 submissions per frame when the game is GPU-bound.

src/d3d11/d3d11_context_imm.cpp

@@ -63,10 +63,6 @@ namespace dxvk {
       return E_INVALIDARG;
     }
     
-    // Flush in order to make sure the query commands get dispatched
-    if ((GetDataFlags & D3D11_ASYNC_GETDATA_DONOTFLUSH) == 0)
-      Flush();
-    
     // Default error return for unsupported interfaces
     HRESULT hr = E_INVALIDARG;