headers: Remove some left-over license text in include/uapi/linux/hsi/

Remove some left-over from commit e2be04c7

 ("License cleanup: add SPDX
license identifier to uapi header files with a license")

When the SPDX-License-Identifier tag has been added, the corresponding
license text has not been removed.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Acked-by: Kai Vehmanen <kvcontact@nosignal.fi>
Acked-by: Peter Ujfalusi <peter.ujfalusi@gmail.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>