bzip2/pbzip2: Correct license information

The license of pbzip2 looks slightly BSD like but is in fact the bzip2
license. The SPDX identifier for this is "bzip-1.0.6" since there is
another version of the bzip license out there.

To clear up all the confusion, use the SPDX license name and update
both recipes to refer to it. The copyright information is slightly
different between the codebases but the license looks the same.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>