s390/atomic_ops: Let __atomic_add_const() variants always return void

Depending on MARCH_HAS_Z196_FEATURES __atomic_add_const() returns void or
the previous value before the atomic variant. Make sure that for both cases
void is returned so potential incorrect usage results in both cases in a
compile error.

Reviewed-by: Juergen Christ <jchrist@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

Author: hcahca

arch/s390/include/asm/atomic_ops.h

@@ -163,10 +163,10 @@ __ATOMIC64_OPS(__atomic64_xor, "xgr")
 
 #undef __ATOMIC64_OPS
 
-#define __atomic_add_const(val, ptr)		__atomic_add(val, ptr)
-#define __atomic_add_const_barrier(val, ptr)	__atomic_add(val, ptr)
-#define __atomic64_add_const(val, ptr)		__atomic64_add(val, ptr)
-#define __atomic64_add_const_barrier(val, ptr)	__atomic64_add(val, ptr)
+#define __atomic_add_const(val, ptr)		((void)__atomic_add(val, ptr))
+#define __atomic_add_const_barrier(val, ptr)	((void)__atomic_add(val, ptr))
+#define __atomic64_add_const(val, ptr)		((void)__atomic64_add(val, ptr))
+#define __atomic64_add_const_barrier(val, ptr)	((void)__atomic64_add(val, ptr))
 
 #endif /* MARCH_HAS_Z196_FEATURES */