mac80211_hwsim: Fix radio dump for radio idx 0

Since 6335698e24ec11e1324b916177da6721df724dd8 the radio with idx of 0
will not get dumped in HWSIM_CMD_GET_RADIO because of the last_idx
checks.  Offset cb->args[0] by 1 similarly to what is done in nl80211.c.

Fixes: 6335698e24ec ("mac80211_hwsim: add generation count for netlink dump operation")
Signed-off-by: Andrew Zaborowski <andrew.zaborowski@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/mac80211_hwsim.c

@@ -3340,7 +3340,7 @@ out_err:
 static int hwsim_dump_radio_nl(struct sk_buff *skb,
 			       struct netlink_callback *cb)
 {
-	int last_idx = cb->args[0];
+	int last_idx = cb->args[0] - 1;
 	struct mac80211_hwsim_data *data = NULL;
 	int res = 0;
 	void *hdr;
@@ -3368,7 +3368,7 @@ static int hwsim_dump_radio_nl(struct sk_buff *skb,
 		last_idx = data->idx;
 	}
 
-	cb->args[0] = last_idx;
+	cb->args[0] = last_idx + 1;
 
 	/* list changed, but no new element sent, set interrupted flag */
 	if (skb->len == 0 && cb->prev_seq && cb->seq != cb->prev_seq) {