syscall: don't use GETREGS/SETREGS on s390

They were removed in recent glibc.

Patch by Andreas Krebbel for GCC PR 81393.

Change-Id: I87be375b9cf760b87aa369ad46cf43831a287a08
Reviewed-on: https://go-review.googlesource.com/48231
Reviewed-by: Ian Lance Taylor <iant@golang.org>
2 files changed