xsk: Fix xsk_poll()'s return type

xsk_poll() is defined as returning 'unsigned int' but the
.poll method is declared as returning '__poll_t', a bitwise type.

Fix this by using the proper return type and using the EPOLL
constants instead of the POLL ones, as required for __poll_t.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Björn Töpel <bjorn.topel@intel.com>
Link: https://lore.kernel.org/bpf/20191120001042.30830-1-luc.vanoostenryck@gmail.com

net/xdp/xsk.c

@@ -447,10 +447,10 @@ static int xsk_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
 	return __xsk_sendmsg(sk);
 }
 
-static unsigned int xsk_poll(struct file *file, struct socket *sock,
+static __poll_t xsk_poll(struct file *file, struct socket *sock,
 			     struct poll_table_struct *wait)
 {
-	unsigned int mask = datagram_poll(file, sock, wait);
+	__poll_t mask = datagram_poll(file, sock, wait);
 	struct sock *sk = sock->sk;
 	struct xdp_sock *xs = xdp_sk(sk);
 	struct net_device *dev;
@@ -472,9 +472,9 @@ static unsigned int xsk_poll(struct file *file, struct socket *sock,
 	}
 
 	if (xs->rx && !xskq_empty_desc(xs->rx))
-		mask |= POLLIN | POLLRDNORM;
+		mask |= EPOLLIN | EPOLLRDNORM;
 	if (xs->tx && !xskq_full_desc(xs->tx))
-		mask |= POLLOUT | POLLWRNORM;
+		mask |= EPOLLOUT | EPOLLWRNORM;
 
 	return mask;
 }