smartdns.conf: correct some typos

etc/smartdns/smartdns.conf

@@ -1,4 +1,4 @@
-# dns server name, defaut is host name
+# dns server name, default is host name
 # server-name, 
 # example:
 #   server-name smartdns
@@ -97,7 +97,7 @@ log-level info
 # dns audit
 # audit-enable [yes|no]: enable or disable audit.
 # audit-enable yes
-# audit-SOA [yes|no]: enable or disalbe log soa result.
+# audit-SOA [yes|no]: enable or disable log soa result.
 # audit-size size of each audit file, support k,m,g
 # audit-file /var/log/smartdns-audit.log
 # audit-size 128k
@@ -164,4 +164,4 @@ log-level info
 #                             speed-check-mode [ping|tcp:port|none|,]
 #   -address [address|-]: same as address option
 #   -nameserver [group|-]: same as nameserver option
-#   -ipset [ipset|-]: same as ipset option
+#   -ipset [ipset|-]: same as ipset option