src/aio-dio-regress/: spdx license conversion

src/aio-dio-regress/: spdx license conversion

The license headers all had to be manually editted into a consistent
format, then converted to spdx tags via scripting.  Manually added
tag to Makefile.

Notes for future reference and research:
- quoted source repositories for aio-dio suite no longer exist
- src/aio-dio-regress/aiodio_sparse2.c has no explicit license
  statement, so need to find original source to determine actual
  license before tagging.

Signed-off-by: Dave Chinner <dchinner@redhat.com>