cmd/compile: clean up arm64 32bit pointer in Reverse
cmd/compile: clean up arm64 32bit pointer in Reverse

Change-Id: I0751270c0f656a501b389f2e2bb0e959d6f5a0e6
Reviewed-on: https://go-review.googlesource.com/c/go/+/396054
Reviewed-by: Keith Randall <8c99c3a9284e493be632950b84cd789d08ed3e9d@golang.org>
Run-TryBot: Keith Randall <8c99c3a9284e493be632950b84cd789d08ed3e9d@golang.org>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Trust: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

CAFxX/go,CAFxX/go,golang/go,CAFxX/go,golang/go,golang/go,golang/go,CAFxX/go,CAFxX/go,golang/go,CAFxX/go,nawawi/go,golang/go,golang/go,golang/go,nawawi/go,nawawi/go,nawawi/go,nawawi/go,CAFxX/go,nawawi/go,nawawi/go,nawawi/go,CAFxX/go