virgl: fix fd leak when map blob resources

In amdgpu renderer export path, if bo with metadata then it will convert to dmabuf type and create a fd copy. But in virgl_renderer_resource_map it will check the export res type and res type, if they are same then do not close fd. In above situation, amdgpu drm backend may cause fd leak.

Use fd_type to record inital fd type, use export_fd_type to record export fd type to prevent fd leak when res type change after export fd.