nft: adapt nft_rule_expr_get to use uint32_t instead of size_t

According to libnftables change 437d610, now the length obtained
via getter function is uint32_t, not size_t anymore.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/iptables/nft-shared.c b/iptables/nft-shared.c
index acf352d..5c09fe1 100644
--- a/iptables/nft-shared.c
+++ b/iptables/nft-shared.c
@@ -223,7 +223,7 @@
 {
 	uint32_t value;
 	const void *ifname;
-	size_t len;
+	uint32_t len;
 
 	switch(key) {
 	case NFT_META_IIF:
@@ -285,7 +285,7 @@
 void nft_parse_target(struct nft_rule_expr *e, struct nft_rule_expr_iter *iter,
 		 int family, void *data)
 {
-	size_t tg_len;
+	uint32_t tg_len;
 	const char *targname = nft_rule_expr_get_str(e, NFT_EXPR_TG_NAME);
 	const void *targinfo = nft_rule_expr_get(e, NFT_EXPR_TG_INFO, &tg_len);
 	struct xtables_target *target;
@@ -316,7 +316,7 @@
 nft_parse_match(struct nft_rule_expr *e, struct nft_rule_expr_iter *iter,
 		struct iptables_command_state *cs)
 {
-	size_t mt_len;
+	uint32_t mt_len;
 	const char *mt_name = nft_rule_expr_get_str(e, NFT_EXPR_MT_NAME);
 	const void *mt_info = nft_rule_expr_get(e, NFT_EXPR_MT_INFO, &mt_len);
 	struct xtables_match *match;
@@ -360,7 +360,7 @@
 {
 	struct nft_rule_expr *e;
 	const char *name;
-	size_t len;
+	uint32_t len;
 	uint8_t op;
 
 	e = nft_rule_expr_iter_next(iter);