busybox: Correct the name of the bzip2 license

The common bzip2 license was renamed from "bzip2" to "bzip2-1.0.6" in
commit 669600ef to match the official SPDX identifier.

Signed-off-by: Peter Kjellerstedt <peter.kjellerstedt@axis.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>