cmd/internal/obj/arm64: fix encoding error for SYS instruction
Currently using the SYS instruction will report the "illegal combination"
error. This is because the assembler parser treats the register operand
as p.To, while optab defines it as p.Reg. This CL fixes this bug.
Change-Id: I57799a7c19934b0c62278948f4efaa41001593a4
Reviewed-on: https://go-review.googlesource.com/c/go/+/396796
Run-TryBot: Eric Fang <eric.fang@arm.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Cherry Mui <cherryyz@google.com>
Trust: Eric Fang <eric.fang@arm.com>