tc: Use correct variable type for get_distribution() result

get_distribution() returns an int.

cppcheck reported:
[tc/q_netem.c:243]: (style) Checking if unsigned variable 'dist_size' is less than zero.

The mismatch actually rendered the error checking
after get_distribution() ineffective.
Signed-off-by: Thomas Jarosch <thomas.jarosch@intra2net.com>

tc/q_netem.c

@@ -125,7 +125,7 @@ static int get_ticks(__u32 *ticks, const char *str)
 static int netem_parse_opt(struct qdisc_util *qu, int argc, char **argv,
 			   struct nlmsghdr *n)
 {
-	size_t dist_size = 0;
+	int dist_size = 0;
 	struct rtattr *tail;
 	struct tc_netem_qopt opt;
 	struct tc_netem_corr cor;