There are two issues in the arm64 assembler.

1. "CMPW $0x22220000, RSP" is encoded to 5b44a4d2ff031b6b, which
   is the combination of "MOVD $0x22220000, Rtmp" and
   "NEGSW Rtmp, ZR".
   The right encoding should be a combination of
   "MOVD $0x22220000, Rtmp" and "CMPW Rtmp, RSP".

2. "AND $0x22220000, R2, RSP" is encoded to 5b44a4d25f601b00,
   which is the combination of "MOVD $0x22220000, Rtmp" and
   an illegal instruction.
   The right behavior should be an error report of
   "illegal combination", since "AND Rtmp, RSP, RSP" is invalid
   in armv8.

This CL fixes the above 2 issues and adds more test cases.

fixes #25557

Change-Id: Ia510be26b58a229f5dfe8a5fa0b35569b2d566e7
Reviewed-on: https://go-review.googlesource.com/114796
Run-TryBot: Ben Shi <powerman1st@163.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>