Handle table attributes in the arm64 kernel map

When getting the arm64 kernel maps sysctl we should look at the table
attributes as well as the block/page attributes. These attributes are
different to the last level attributes so need to be translated.

The previous code assumed the table and block/page attributes are
identical, however this is not the case. Handle the difference by
extracting the code into new helper functions & calling them as needed
based on the entry type being checked.

Reviewed by: markj
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D33321