nbd-client: Use correct macro parenthesization

If 'bs' is a complex expression, we were only casting the front half
rather than the full expression.  Luckily, none of the callers were
passing bad arguments, but it's better to be robust up front.
Signed-off-by: NEric Blake <eblake@redhat.com>
Message-Id: <20170918214649.17550-1-eblake@redhat.com>
Reviewed-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>

block/nbd-client.c

@@ -31,8 +31,8 @@
 #include "qapi/error.h"
 #include "nbd-client.h"
 
-#define HANDLE_TO_INDEX(bs, handle) ((handle) ^ ((uint64_t)(intptr_t)bs))
-#define INDEX_TO_HANDLE(bs, index)  ((index)  ^ ((uint64_t)(intptr_t)bs))
+#define HANDLE_TO_INDEX(bs, handle) ((handle) ^ (uint64_t)(intptr_t)(bs))
+#define INDEX_TO_HANDLE(bs, index)  ((index)  ^ (uint64_t)(intptr_t)(bs))
 
 static void nbd_recv_coroutines_wake_all(NBDClientSession *s)
 {