bpf: encapsulate verifier log state into a structure

bpf: encapsulate verifier log state into a structure

Put the loose log_* variables into a structure.  This will make
it simpler to remove the global verifier state in following patches.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>