[S390] implement is_compat_task

Implement is_compat_task and use it all over the place.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c
index a3acd8e..355f7a3 100644
--- a/arch/s390/kernel/process.c
+++ b/arch/s390/kernel/process.c
@@ -32,6 +32,7 @@
 #include <linux/elfcore.h>
 #include <linux/kernel_stat.h>
 #include <linux/syscalls.h>
+#include <asm/compat.h>
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
 #include <asm/system.h>
@@ -204,7 +205,7 @@
 	save_fp_regs(&p->thread.fp_regs);
 	/* Set a new TLS ?  */
 	if (clone_flags & CLONE_SETTLS) {
-		if (test_thread_flag(TIF_31BIT)) {
+		if (is_compat_task()) {
 			p->thread.acrs[0] = (unsigned int) regs->gprs[6];
 		} else {
 			p->thread.acrs[0] = (unsigned int)(regs->gprs[6] >> 32);