This makes the runtime.support_sse2 variable unused
so it is removed in this CL too.

Change-Id: Ia8b9ffee7ac97128179f74ef244b10315e44c234
Reviewed-on: https://go-review.googlesource.com/131455
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>