ospfd: Some small tweaks to the SPF execution reason patch

* ospf_spf.h: use an enum for the reason, and have it as a new argument to
  ospf_spf_calculate_schedule, no need for additional call, and let compiler
  do the checking.
* ospf_spf.c: format changes - Quagga coding style places function names
  at the start of a new line, for easy grepping for definition.
  (ospf_spf_calculate_timer) Change the log format of SPF execution time to
  avoid ginormous line, and make logging conditional, as is the norm.
diff --git a/ospfd/ospf_vty.c b/ospfd/ospf_vty.c
index 5674da0..72493a2 100644
--- a/ospfd/ospf_vty.c
+++ b/ospfd/ospf_vty.c
@@ -771,7 +771,7 @@
 	{
 	  vl_data->vl_oi = ospf_vl_new (ospf, vl_data);
 	  ospf_vl_add (ospf, vl_data);
-	  ospf_spf_calculate_schedule (ospf);
+	  ospf_spf_calculate_schedule (ospf, SPF_FLAG_CONFIG_CHANGE);
 	}
     }
   return vl_data;
@@ -2172,7 +2172,7 @@
   if (!CHECK_FLAG (ospf->config, OSPF_RFC1583_COMPATIBLE))
     {
       SET_FLAG (ospf->config, OSPF_RFC1583_COMPATIBLE);
-      ospf_spf_calculate_schedule (ospf);
+      ospf_spf_calculate_schedule (ospf, SPF_FLAG_CONFIG_CHANGE);
     }
   return CMD_SUCCESS;
 }
@@ -2189,7 +2189,7 @@
   if (CHECK_FLAG (ospf->config, OSPF_RFC1583_COMPATIBLE))
     {
       UNSET_FLAG (ospf->config, OSPF_RFC1583_COMPATIBLE);
-      ospf_spf_calculate_schedule (ospf);
+      ospf_spf_calculate_schedule (ospf, SPF_FLAG_CONFIG_CHANGE);
     }
   return CMD_SUCCESS;
 }