IB/core: Reduce the places that use zgid

Instead of open coding memcmp() to check whether a given GID is zero or
not, use a helper function to do so, and replace instances of
memcpy(z,&zgid) with memset.

Signed-off-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/mlx4/main.c

@@ -276,7 +276,7 @@ static int mlx4_ib_add_gid(const union ib_gid *gid,
 			found = i;
 			break;
 		}
-		if (free < 0 && !memcmp(&port_gid_table->gids[i].gid, &zgid, sizeof(*gid)))
+		if (free < 0 && rdma_is_zero_gid(&port_gid_table->gids[i].gid))
 			free = i; /* HW has space */
 	}
 
@@ -345,7 +345,8 @@ static int mlx4_ib_del_gid(const struct ib_gid_attr *attr, void **context)
 		if (!ctx->refcount) {
 			unsigned int real_index = ctx->real_index;
 
-			memcpy(&port_gid_table->gids[real_index].gid, &zgid, sizeof(zgid));
+			memset(&port_gid_table->gids[real_index].gid, 0,
+			       sizeof(port_gid_table->gids[real_index].gid));
 			kfree(port_gid_table->gids[real_index].ctx);
 			port_gid_table->gids[real_index].ctx = NULL;
 			hw_update = 1;

drivers/infiniband/hw/mlx4/qp.c

@@ -3078,7 +3078,7 @@ static int fill_gid_by_hw_index(struct mlx4_ib_dev *ibdev, u8 port_num,
 	memcpy(gid, &port_gid_table->gids[index].gid, sizeof(*gid));
 	*gid_type = port_gid_table->gids[index].gid_type;
 	spin_unlock_irqrestore(&iboe->lock, flags);
-	if (!memcmp(gid, &zgid, sizeof(*gid)))
+	if (rdma_is_zero_gid(gid))
 		return -ENOENT;
 
 	return 0;