MAINTAINERS: add crc_kunit.c back to CRC LIBRARY

Restore lib/tests/crc_kunit.c to CRC LIBRARY following the rename in
commit db6fe4d6 ("lib: Move KUnit tests into tests/ subdirectory")
which made it no longer match the file pattern lib/crc*.

Reviewed-by: Kees Cook <kees@kernel.org>
Link: https://lore.kernel.org/r/20250511052151.420228-1-ebiggers@kernel.org


Signed-off-by: Eric Biggers <ebiggers@google.com>