cmd/compile/internal/s390x: cleanup betypeinit

The Width{int,ptr,reg} assignments are no longer necessary since
golang.org/cl/21623. The other arch's betypeinit functions were
cleaned up, but apparently this one was missed.

Change-Id: I1c7f074d7864a561659c1f98aef604f57f285fd0
Reviewed-on: https://go-review.googlesource.com/27272
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Michael Munday <munday@ca.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/compile/internal/s390x/galign.go

@@ -10,9 +10,6 @@ import (
 )
 
 func betypeinit() {
-	gc.Widthptr = 8
-	gc.Widthint = 8
-	gc.Widthreg = 8
 }
 
 func Main() {