cmd/internal/obj/arm64: use more appropriate types for olsr12u
This allows for a large number of casts to be removed at call sites.
Change-Id: Id929f6c7155b0b59a2bcdf43144de95a007b8a48
Reviewed-on: https://go-review.googlesource.com/c/go/+/461139
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Than McIntosh <thanm@google.com> Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Joel Sing <joel@sing.id.au> Reviewed-by: Eric Fang <eric.fang@arm.com>