cmd/asm/internal/asm: update the test cases in arm64enc.s file

Uncomment the test cases in arm64enc.s because they can be handled
by current assembler. In addition, CL supplements more test cases.

Change-Id: I583d45793b8227c6ec370868652dd8bcbfaa1ecf
Reviewed-on: https://go-review.googlesource.com/109275Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>