Remove support for keyed MD5 and SHA1 authentication hashes.

They no longer have any in-tree consumers. Note that these are a
different from MD5-HMAC and SHA1-HMAC and were only used with IPsec.

Reviewed by: cem
Relnotes: yes
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D24770