libobs-d3d11: Fix potential issue rebuilding shared texture

Sometimes when rebuilding a texture, it often has to fall back and
create a temporary texture, but it'll fail when trying to create a
shader resource for it.  The suspicion is because it's due to not having
the proper shader binding flag when creating that temporary texture, so
this fixes that possible loophole.

libobs-d3d11/d3d11-rebuild.cpp

@@ -40,6 +40,7 @@ void gs_texture_2d::RebuildSharedTextureFallback()
 	td.Format           = DXGI_FORMAT_B8G8R8A8_UNORM;
 	td.ArraySize        = 1;
 	td.SampleDesc.Count = 1;
+	td.BindFlags        = D3D11_BIND_SHADER_RESOURCE;
 
 	width      = td.Width;
 	height     = td.Height;