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_abr.c b/ospfd/ospf_abr.c
index ca1af2c..e172e53 100644
--- a/ospfd/ospf_abr.c
+++ b/ospfd/ospf_abr.c
@@ -556,8 +556,7 @@
 
   if (new_flags != ospf->flags)
     {
-      ospf_flag_spf_reason (SPF_FLAG_ABR_STATUS_CHANGE);
-      ospf_spf_calculate_schedule (ospf);
+      ospf_spf_calculate_schedule (ospf, SPF_FLAG_ABR_STATUS_CHANGE);
       if (IS_DEBUG_OSPF_EVENT)
 	zlog_debug ("ospf_check_abr_status(): new router flags: %x",new_flags);
       ospf->flags = new_flags;