selftests: net: netlink-dumps: validation checks

The sanity checks are going to get silently cast to unsigned
and always pass. Cast the sizeof to signed size.

Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20241115003248.733862-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

tools/testing/selftests/net/netlink-dumps.c

@@ -56,10 +56,10 @@ TEST(test_sanity)
 	ASSERT_EQ(n, sizeof(dump_policies));
 
 	n = recv(netlink_sock, buf, sizeof(buf), MSG_DONTWAIT);
-	ASSERT_GE(n, sizeof(struct nlmsghdr));
+	ASSERT_GE(n, (ssize_t)sizeof(struct nlmsghdr));
 
 	n = recv(netlink_sock, buf, sizeof(buf), MSG_DONTWAIT);
-	ASSERT_GE(n, sizeof(struct nlmsghdr));
+	ASSERT_GE(n, (ssize_t)sizeof(struct nlmsghdr));
 
 	close(netlink_sock);
 }