unit: remove duplicated invalid definitions in test-snep-read

The unit tests duplicated several definitions in unit/test-utils.h which
after some time become outdated and not matching the original ones.
This lead to bogus data printed in logs, for example length of
near_ndef_record:

    [SNEP unit]	dummy_req_put STORED REC data=0x55ceb3fc8050 length=94346271294192

Move all of them into new src/ndef-private.h header.  Start using SPDX
identifier instead of full GPL license boilerplate.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
5 files changed