fsdev: Drop unused opaque field

This was introduced along with -fsdev but it never got used.

Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>

fsdev/file-op-9p.h

@@ -147,7 +147,6 @@ struct FileOperations
     int (*renameat)(FsContext *ctx, V9fsPath *olddir, const char *old_name,
                     V9fsPath *newdir, const char *new_name);
     int (*unlinkat)(FsContext *ctx, V9fsPath *dir, const char *name, int flags);
-    void *opaque;
 };
 
 #endif