[S390] clear_table inline assembly contraints

Tell the compile that the clear_table inline assembly writes to the
memory referenced by *s.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/pgalloc.h

@@ -28,6 +28,8 @@ void disable_noexec(struct mm_struct *, struct task_struct *);
 
 static inline void clear_table(unsigned long *s, unsigned long val, size_t n)
 {
+	typedef struct { char _[n]; } addrtype;
+
 	*s = val;
 	n = (n / 256) - 1;
 	asm volatile(
@@ -39,7 +41,8 @@ static inline void clear_table(unsigned long *s, unsigned long val, size_t n)
 		"0:	mvc	256(256,%0),0(%0)\n"
 		"	la	%0,256(%0)\n"
 		"	brct	%1,0b\n"
-		: "+a" (s), "+d" (n));
+		: "+a" (s), "+d" (n), "=m" (*(addrtype *) s)
+		: "m" (*(addrtype *) s));
 }
 
 static inline void crst_table_init(unsigned long *crst, unsigned long entry)