cmd/internal/obj/arm64: move register encoding into opxrrr
Rather than having register encoding knowledge in each caller of opxrrr,
pass the registers into opxrrr and let it handle the encoding. This reduces
duplication and improves readability.
Change-Id: I202c503465a0169277a0f64340598203c9dcf20c
Reviewed-on: https://go-review.googlesource.com/c/go/+/461140
Run-TryBot: Joel Sing <joel@sing.id.au> Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Cherry Mui <cherryyz@google.com>