pacakge/iw: don't show a stray ']' if the chain signal attribute list is empty

Without the patch, the output of 'station dump' command looks weird in
some cases:

root@OpenWrt:/# iw dev wlan0 station dump
Station 00:21:27:cb:57:02 (on wlan0)
        inactive time:  190 ms
        rx bytes:       36652
        rx packets:     149
        tx bytes:       1998
        tx packets:     16
        tx retries:     0
        tx failed:      0
        signal:         -31 ] dBm
        signal avg:     -30 [-32, -36] dBm
        tx bitrate:     5.5 MBit/s
        rx bitrate:     54.0 MBit/s
root@OpenWrt:/#

SVN-Revision: 28879

package/iw/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=iw
 PKG_VERSION:=3.1
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.bz2
 PKG_SOURCE_URL:=http://wireless.kernel.org/download/iw/

package/iw/patches/120-per_chain_signal_strength.patch

@@ -1,6 +1,6 @@
 --- a/station.c
 +++ b/station.c
-@@ -61,6 +61,31 @@ static void print_sta_bitrate(struct nla
+@@ -61,6 +61,33 @@ static void print_sta_bitrate(struct nla
  	}
  }
  
@@ -24,7 +24,9 @@
 +		cur += snprintf(cur, sizeof(buf) - (cur - buf), "%s%d", prefix,
 +				(int8_t) nla_get_u8(attr));
 +	}
-+	snprintf(cur, sizeof(buf) - (cur - buf), "] ");
++
++	if (i)
++		snprintf(cur, sizeof(buf) - (cur - buf), "] ");
 +
 +	return buf;
 +}
@@ -32,7 +34,7 @@
  static int print_sta_handler(struct nl_msg *msg, void *arg)
  {
  	struct nlattr *tb[NL80211_ATTR_MAX + 1];
-@@ -81,7 +106,10 @@ static int print_sta_handler(struct nl_m
+@@ -81,7 +108,10 @@ static int print_sta_handler(struct nl_m
  		[NL80211_STA_INFO_PLINK_STATE] = { .type = NLA_U8 },
  		[NL80211_STA_INFO_TX_RETRIES] = { .type = NLA_U32 },
  		[NL80211_STA_INFO_TX_FAILED] = { .type = NLA_U32 },
@@ -43,7 +45,7 @@
  
  	nla_parse(tb, NL80211_ATTR_MAX, genlmsg_attrdata(gnlh, 0),
  		  genlmsg_attrlen(gnlh, 0), NULL);
-@@ -128,12 +156,18 @@ static int print_sta_handler(struct nl_m
+@@ -128,12 +158,18 @@ static int print_sta_handler(struct nl_m
  	if (sinfo[NL80211_STA_INFO_TX_FAILED])
  		printf("\n\ttx failed:\t%u",
  			nla_get_u32(sinfo[NL80211_STA_INFO_TX_FAILED]));