lkl: Check for POLLPRI in POSIX net_poll

Strictly speaking, POSIX.1-2008 in the poll.h entry says:

   POLLIN
      Data other than high priority data may be read without blocking

   POLLPRI
      Priority data may be read without blocking

So to check that we can read(2) without blocking, we should check for
POLLPRI in addition to POLLIN.

Signed-off-by: Patrick Collins <pscollins@google.com>

tools/lkl/lib/posix-host.c

@@ -304,7 +304,7 @@ static int net_poll(union lkl_netdev nd, int events)
 	int ret = 0;
 
 	if (events & LKL_DEV_NET_POLL_RX)
-		pfd.events |= POLLIN;
+		pfd.events |= POLLIN | POLLPRI;
 	if (events & LKL_DEV_NET_POLL_TX)
 		pfd.events |= POLLOUT;