bash-completion: update cfdisk

Signed-off-by: Karel Zak <kzak@redhat.com>
bash-completion: update fallocate, fstrim and lsblk

Signed-off-by: Karel Zak <kzak@redhat.com>
docs: add note about lsblk

Signed-off-by: Karel Zak <kzak@redhat.com>