cmd/asm: Add SHA3 hardware instructions for ARM64

Armv8.2-SHA introduced four SHA3-related instructions

EOR3 <Vd>.16B, <Vn>.16B, <Vm>.16B, <Va>.16B
RAX1 <Vd>.2D, <Vn>.2D, <Vm>.2D
XAR <Vd>.2D, <Vn>.2D, <Vm>.2D, #<imm6>
BCAX <Vd>.16B, <Vn>.16B, <Vm>.16B, <Va>.16B

We convert them into Go asm style as:

VEOR3 <Va>.B16, <Vm>.B16, <Vn>.B16, <Vd>.B16
VRAX1 <Vm>.D2, <Vn>.D2, <Vd>.D2
VXAR $imm6, <Vm>.D2, <Vn>.D2, <Vd>.D2
VBCAX <Va>.B16, <Vm>.B16, <Vn>.B16, <Vd>.B16

Armv8 Reference Manual:
* EOR3 (Three-way Exclusive OR) on C7.2.42
* RAX1 (Rotate and Exclusive OR) on C7.2.217
* XAR (Exclusive OR and Rotate) on C7.2.401
* BCAX (Bit Clear and Exclusive OR) on C7.2.12

Change-Id: I9a5d1b5ad508ed8fd5289d535906c54d9a63ca5a
Reviewed-on: https://go-review.googlesource.com/c/go/+/180757


Run-TryBot: Meng Zhuo <mzh@golangcn.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Trust: Emmanuel Odeke <emm.odeke@gmail.com>