arm64/disassem.c: Add shifted register instruction definitions
Add disassembly support for the following shifted register instructions:
- adds
- subs
- sub
- neg
- negs
- cmp
- cmn
The 'Mandatory Tokens' checks are relaxed to allow for the alias
instructions (e.g. cmp) which hard-code one or more registers as xzr.
Reviewed by: mhorne
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D40006
(cherry picked from commit ffa75b573f043951c7958c200c1e0e1b1f703740)