It is usual that we need to check if one BPF insn is for loading/storeing
data from/to memory.

Therefore, it makes sense to factor out related code to become common
helper functions.
Signed-off-by: NJiong Wang <jiong.wang@netronome.com>
Reviewed-by: NJakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>