cmd/asm: fix condition check to work on ppc64
A condition check was added to parse.go in CL 405542 to prevent
usage of scaled operands on ppc64. However while trying to improve
the error notification message, an if-condition was left out by
oversight. This CL corrects that.
Change-Id: I8cef3dd194c75343354ffe888b5e639e694badde
Reviewed-on: https://go-review.googlesource.com/c/go/+/426994
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Archana Ravindar <aravind5@in.ibm.com>
Reviewed-by: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>