selftests: xsx: Introduce test name in test spec

Introduce the test name in the test specification. This so we can set
the name locally in the test function and simplify the logic for
printing out test results.

Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Link: https://lore.kernel.org/bpf/20210907071928.9750-8-magnus.karlsson@gmail.com