Always include <config.h> in cipher assembly codes

* cipher/poly1305-s390x.S: Always include <config.h>.

When Intel CET is enabled, we need to include <cet.h> in assembly codes
to mark Intel CET support even if it is empty. We should always include
<config.h> in cipher assembly codes so that they will be marked for
Intel CET support when compiling for x86-64 and i686.

• Signed-off-by: H.J. Lu <hjl.tools@gmail.com>