bpf/tests: Enhance output on error and fix typos

If a testcase returns a wrong (unexpected) value, print the expected and
returned value in hex notation in addition to the decimal notation.

This is very useful in tests which bit-shift hex values left or right and
helped me a lot while developing the JIT compiler for the hppa architecture.

Additionally fix two typos: dowrd -> dword, tall calls -> tail calls.

Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/ZN6ZAAVoWZpsD1Jf@p100