Merge branch 'bpf-subreg-tests'

Jiong Wang says:

====================
JIT back-ends need to guarantee high 32-bit cleared whenever one eBPF insn
write low 32-bit sub-register only. It is possible that some JIT back-ends
have failed doing this and are silently generating wrong image.

This set completes the unit tests, so bug on this could be exposed in JITs.
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>