IB/mlx4: Convert is_xxx variables in build_mlx_header() to bool

Matches the way they're used, and actually lets at least x86-64 generate
better code:

    add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-38 (-38)
    function                                     old     new   delta
    mlx4_ib_post_send                           4416    4378     -38
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/hw/mlx4/mlx4_ib.h

@@ -652,12 +652,12 @@ int __mlx4_ib_query_gid(struct ib_device *ibdev, u8 port, int index,
 int mlx4_ib_resolve_grh(struct mlx4_ib_dev *dev, const struct ib_ah_attr *ah_attr,
 			u8 *mac, int *is_mcast, u8 port);
 
-static inline int mlx4_ib_ah_grh_present(struct mlx4_ib_ah *ah)
+static inline bool mlx4_ib_ah_grh_present(struct mlx4_ib_ah *ah)
 {
 	u8 port = be32_to_cpu(ah->av.ib.port_pd) >> 24 & 3;
 
 	if (rdma_port_get_link_layer(ah->ibah.device, port) == IB_LINK_LAYER_ETHERNET)
-		return 1;
+		return true;
 
 	return !!(ah->av.ib.g_slid & 0x80);
 }

drivers/infiniband/hw/mlx4/qp.c

@@ -1746,11 +1746,11 @@ static int build_mlx_header(struct mlx4_ib_sqp *sqp, struct ib_send_wr *wr,
 	int header_size;
 	int spc;
 	int i;
-	int is_eth;
-	int is_vlan = 0;
-	int is_grh;
-	u16 vlan;
 	int err = 0;
+	u16 vlan;
+	bool is_eth;
+	bool is_vlan = false;
+	bool is_grh;
 
 	send_size = 0;
 	for (i = 0; i < wr->num_sge; ++i)