IB/mad: Fix sparse warning about gfp_t use

Properly convert gfp_t & result to bool to fix:

    drivers/infiniband/core/sa_query.c:621:33: warning: incorrect type in initializer (different base types)
    drivers/infiniband/core/sa_query.c:621:33:    expected bool [unsigned] [usertype] preload
    drivers/infiniband/core/sa_query.c:621:33:    got restricted gfp_t
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/core/sa_query.c

@@ -618,7 +618,7 @@ static void init_mad(struct ib_sa_mad *mad, struct ib_mad_agent *agent)
 
 static int send_mad(struct ib_sa_query *query, int timeout_ms, gfp_t gfp_mask)
 {
-	bool preload = gfp_mask & __GFP_WAIT;
+	bool preload = !!(gfp_mask & __GFP_WAIT);
 	unsigned long flags;
 	int ret, id;