AArch64: Remove unused instructions

As these aren't ever emitted, we don't even know if they work or will
ever be used. If one of them is needed in future, we may easily re-add
it.

Deleted instructions are:
- CMN
- ANDS
- BIC
- BICS
- EON
- ORN
- ROR
- TST
- STP
- LDP
- DMBSY