ddb: improve printing of inpcbs

• shuffle around the inp_label to give inp_flags more space since it can become long.
• fix the indentation of in6p_icmp6filt, in6p_cksum, and in6p_hops.

Reviewed by: Peter Lei
MFC after: 3 days
Sponsored by: Netflix, Inc.
Differential Revision: https://reviews.freebsd.org/D53541