microsoft/resource_state_manager: Remove unused private variable

Clang detects that this variable is unused. We can re-add it if
we end up needing it but for now let's just remove it.
Reviewed-by: Adam Jackson <ajax@redhat.com>
Part-of: <mesa/mesa!8248>

src/microsoft/resource_state_manager/D3D12ResourceState.h

@@ -146,7 +146,6 @@ struct TransitionableResourceState
    TransitionableResourceState(ID3D12Resource *pResource, UINT TotalSubresources, bool SupportsSimultaneousAccess) :
       m_DesiredState(TotalSubresources),
       m_TotalSubresources(TotalSubresources),
-      m_SupportsSimultaneousAccess(SupportsSimultaneousAccess),
       m_currentState(TotalSubresources, SupportsSimultaneousAccess),
       m_pResource(pResource)
    {
@@ -171,7 +170,6 @@ struct TransitionableResourceState
 
 private:
    unsigned m_TotalSubresources;
-   bool m_SupportsSimultaneousAccess;
 
    CCurrentResourceState m_currentState;