tools/libacpi: Re-licence remaining GPL code to LGPLv2.1

tools/libacpi: Re-licence remaining GPL code to LGPLv2.1

We now have permission from Lenovo to relicense commit 801d469ad8b2
("[HVM] ACPI support patch 3 of 4: ACPI _PRT table") to LGPLv2.1

This essentially means reverting commits c3397311a658 ("acpi: Prevent
GPL-only code from seeping into non-GPL binaries") and 26c4f0b8a4cf
("tools/libacpi: fix sed usage")

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Acked-by: Ken Lancaster <klancaster@lenovo.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Wei Liu <wei.liu2@citrix.com>