cmd/compile: use jump table on ARM64

cmd/compile: use jump table on ARM64

Following CL 357330, use jump tables on ARM64.

name                         old time/op  new time/op  delta
Switch8Predictable-4         3.41ns ± 0%  3.21ns ± 0%     ~     (p=0.079 n=4+5)
Switch8Unpredictable-4       12.0ns ± 0%   9.5ns ± 0%  -21.17%  (p=0.000 n=5+4)
Switch32Predictable-4        3.06ns ± 0%  2.82ns ± 0%   -7.78%  (p=0.008 n=5+5)
Switch32Unpredictable-4      13.3ns ± 0%   9.5ns ± 0%  -28.87%  (p=0.016 n=4+5)
SwitchStringPredictable-4    3.71ns ± 0%  3.21ns ± 0%  -13.43%  (p=0.000 n=5+4)
SwitchStringUnpredictable-4  14.8ns ± 0%  15.1ns ± 0%   +2.37%  (p=0.008 n=5+5)

Change-Id: Ia0b85df7ca9273cf70c05eb957225c6e61822fa6
Reviewed-on: https://go-review.googlesource.com/c/go/+/403979
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: David Chase <drchase@google.com>