Merge branch 'bpf-verifier-misc-improvements'

Alexei Starovoitov says:

====================
Small set of verifier improvements and cleanups which is
necessary for bigger patch set of bpf-to-bpf calls coming later.
See individual patches for details.
Tested on x86 and arm64 hw.
====================

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