Adopt the license text suggested by Guan Xue-tao (with a minor
simplification) for all target-unicore/ files except helper.c.

To helper.c Anthony Liguori contributed a qemu_malloc() -> g_malloc()
conversion, still pending IBM relicensing approval, so that remains
GPLv2 for now.

By relicensing all possible parts now, we avoid having to formally
relicense new, e.g., QOM code.

Signed-off-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Guan Xuetao <gxt@mprc.pku.edu.cn>
Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
Signed-off-by: Dor Laor <dlaor@redhat.com>