[IPV4] display bootserver in /proc/net/pnp

With modification from niv@us.ibm.com to only print
bootserver if there was one.

net/ipv4/ipconfig.c

@@ -1115,6 +1115,10 @@ static int pnp_get_info(char *buffer, char **start,
 				       "nameserver %u.%u.%u.%u\n",
 				       NIPQUAD(ic_nameservers[i]));
 	}
+	if (ic_servaddr != INADDR_NONE)
+		len += sprintf(buffer + len,
+			       "bootserver %u.%u.%u.%u\n",
+			       NIPQUAD(ic_servaddr));
 
 	if (offset > len)
 		offset = len;