target/s390x: mask the SIGP order_code using SIGP_ORDER_MASK

For that move the definition from kvm.c to cpu.h

Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Message-Id: <20170509082800.10756-2-aurelien@aurel32.net>
Signed-off-by: Richard Henderson <rth@twiddle.net>