[zebra] fix inconsistencies in ifstat_update_* declarations and definitions

[zebra] fix inconsistencies in ifstat_update_* declarations and definitions

2006-08-06 Paul Jakma <paul.jakma@sun.com>

	* interface.h: (ifstat_update_proc) declaration should match
	  ifstat_update_sysctl really, which is to not return status, as
	  such status is not used anywhere.
	* if_{proc,sysctl}.c: Make ifstat_update_* definitions and return values
	  consistent with each other and their declarations, ie:
	  (void) (*) (void).