[PATCH] selftests/xsk: Fix unsigned comparison with less than zero

poll() may return negative on error, 'ret' should be int.

Fixes: 3143d10b0945 ("selftests/xsk: Update poll test cases")
Signed-off-by: YueHaibing <redacted>
---
 tools/testing/selftests/bpf/xskxceiver.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/xskxceiver.c b/tools/testing/selftests/bpf/xskxceiver.c
index 681a5db80dae..162d3a516f2c 100644
--- a/tools/testing/selftests/bpf/xskxceiver.c
+++ b/tools/testing/selftests/bpf/xskxceiver.c

@@ -1006,7 +1006,8 @@ static int __send_pkts(struct ifobject *ifobject, u32 *pkt_nb, struct pollfd *fd
 {
 	struct xsk_socket_info *xsk = ifobject->xsk;
 	bool use_poll = ifobject->use_poll;
-	u32 i, idx = 0, ret, valid_pkts = 0;
+	u32 i, idx = 0, valid_pkts = 0;
+	int ret;
 
 	while (xsk_ring_prod__reserve(&xsk->tx, BATCH_SIZE, &idx) < BATCH_SIZE) {
 		if (use_poll) {