RDMA/cma: Fix initialization of next_port

next_port should be between sysctl_local_port_range[0] and [1].
However, it is initially set to a random value with get_random_bytes().  
If the value is negative when treated as a signed integer, next_port
can end up outside the expected range because of the result of the % 
operator being negative.
Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/core/cma.c

@@ -2773,8 +2773,8 @@ static int cma_init(void)
 	int ret;
 
 	get_random_bytes(&next_port, sizeof next_port);
-	next_port = (next_port % (sysctl_local_port_range[1] -
-				  sysctl_local_port_range[0])) +
+	next_port = ((unsigned int) next_port %
+		    (sysctl_local_port_range[1] - sysctl_local_port_range[0])) +
 		    sysctl_local_port_range[0];
 	cma_wq = create_singlethread_workqueue("rdma_cm");
 	if (!cma_wq)