Also print symbols when printing arm64 registers

When printing arm64 registers because of an exception in the kernel
also print the symbol and offset. This can be used to track down why
the exception occured without needing external tools.

Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D32077

(cherry picked from commit 7ec86b66099124a9c2c88613507a10979cb8b191)