We have several headers that are including themselves, triggering clangd
warnings.
Such includes are caused by commit 602035d7 ("btrfs: add forward
declarations and headers, part 2").

Just remove such unnecessary include.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>