asm-generic: Add missing brackets for io_stop_wc macro

After using io_stop_wc(), drivers reports following compile error when
compiled on X86.

  drivers/net/ethernet/hisilicon/hns3/hns3_enet.c: In function ‘hns3_tx_push_bd’:
  drivers/net/ethernet/hisilicon/hns3/hns3_enet.c:2058:12: error: expected ‘;’ before ‘(’ token
    io_stop_wc();
              ^
It is because I missed to add the brackets after io_stop_wc macro. So
let's add the missing brackets.

Fixes: d5624bb2 ("asm-generic: introduce io_stop_wc() and add implementation for ARM64")
Reported-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Link: https://lore.kernel.org/r/20220114105857.126300-1-wangxiongfeng2@huawei.comSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>

include/asm-generic/barrier.h

@@ -259,7 +259,7 @@ do {									\
  * write-combining memory accesses before this macro with those after it.
  */
 #ifndef io_stop_wc
-#define io_stop_wc do { } while (0)
+#define io_stop_wc() do { } while (0)
 #endif
 
 #endif /* !__ASSEMBLY__ */