padlock.4: Update slightly for 64-bit hardware

• Change the document description to "Via and Zhaoxin CPU crypto driver"
• Add a HARDWARE section mentioning these in the hardware release note

This manual still needs desperate help, but just this little bit could
have saved a lot of confusion. I'd write more if I had information.

PR: 295517
Fixes: 14b8531c4ccb8 (Restore padlock_rng the the amd64 build)
MFC after: 3 days (to 15 only)
Reviewed by: bcr, asomers
Differential Revision: https://reviews.freebsd.org/D57920

(cherry picked from commit 380c6f59c4f87dbc45a67983d927700ca7e22be2)