IB/core: type promotion bug in rdma_rw_init_one_mr()

"nents" is an unsigned int, so if ib_map_mr_sg() returns a negative
error code then it's type promoted to a high unsigned int which is
treated as success.

Fixes: a060b562 ("IB/core: generic RDMA READ/WRITE API")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/rw.c

@@ -87,7 +87,7 @@ static int rdma_rw_init_one_mr(struct ib_qp *qp, u8 port_num,
 	}
 
 	ret = ib_map_mr_sg(reg->mr, sg, nents, &offset, PAGE_SIZE);
-	if (ret < nents) {
+	if (ret < 0 || ret < nents) {
 		ib_mr_pool_put(qp, &qp->rdma_mrs, reg->mr);
 		return -EINVAL;
 	}