geom_ccd.c: Update the license with changes from upstream.

Part of this file originated in NetBSD, with the original file
carrying two versions of 4-clause BSD licenses. r109471 attempted to
simplify the situation by putting both licenses together.

Meanwhile, NetBSD dropped Clauses 3 and 4 from their own license, and
eventually NetBSD got permission from the University of Utah to drop the
3rd clause.

Keep the license "simple" by dropping the third clause since both TNF,
Utah/Berkeley and phk agree in principle that it can be dropped.

Obtained from: NetBSD (ccd.c CVS 1.128, 1.138)