peripheral: Add SPDX License Identifier

peripheral: Add SPDX License Identifier

This patch adds SPDX License Identifier and removes the license text.

-------------------------------------
       License            COUNT
-------------------------------------
 LGPL-2.1-or-later    :     11

License: LGPL-2.1-or-later
   peripheral/log.h
   peripheral/main.c
   peripheral/efivars.c
   peripheral/attach.h
   peripheral/gatt.c
   peripheral/attach.c
   peripheral/log.c
   peripheral/gap.h
   peripheral/efivars.h
   peripheral/gap.c
   peripheral/gatt.h

Signed-off-by: Anuj Jain <anuj01.jain@samsung.com>
Signed-off-by: Ayush Garg <ayush.garg@samsung.com>