s390/compat: fix compile error for !COMPAT

Fix this one for !COMPAT:

compat.h: In function ‘arch_compat_alloc_user_space’:
compat.h:292:2: error: implicit declaration of function ‘is_compat_task’

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/compat.h b/arch/s390/include/asm/compat.h
index d967ac8..1f1a449 100644
--- a/arch/s390/include/asm/compat.h
+++ b/arch/s390/include/asm/compat.h
@@ -248,8 +248,6 @@
 	return is_32bit_task();
 }
 
-#endif
-
 static inline void __user *arch_compat_alloc_user_space(long len)
 {
 	unsigned long stack;
@@ -260,6 +258,8 @@
 	return (void __user *) (stack - len);
 }
 
+#endif
+
 struct compat_ipc64_perm {
 	compat_key_t key;
 	__compat_uid32_t uid;