libbsd: Add correct license for all packages

libbsd: Add correct license for all packages

BSD-4-Clause is only applicable to the {PN}-doc package as when I
check for the source code I find below files which only uses the
license BSD-4-Clause

~/sources/libbsd$ grep -rl "All advertising materials mentioning features or use of this software" *|grep -v \.1|grep -v \.5|grep -v \.8 | sort
COPYING
man/arc4random.3bsd
man/getprogname.3bsd
man/tree.3bsd

~/sources/libbsd$ grep -rnB6 "BSD-4"
COPYING-9-Files:
COPYING-10- man/arc4random.3bsd
COPYING-11- man/tree.3bsd
COPYING-12-Copyright:
COPYING-13- Copyright 1997 Niels Provos <provos@physnet.uni-hamburg.de>
COPYING-14- All rights reserved.
COPYING:15:License: BSD-4-clause-Niels-Provos

Signed-off-by: Steve Sakoman <steve@sakoman.com>