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.
