arm64: Update the ID_AA64ISAR1_EL1 fields

While here move to decimal for the _op and _CR definitions to be used
by a future macro to define the register when the assembler doesn't
know about it.

Sponsored by: Arm Ltd
Differential Revision: https://reviews.freebsd.org/D40889

(cherry picked from commit de01309926e21e1cff196b6b23cff6c52064aa0e)