Change CPU time statistics (cputime) to be accounted on a per-CPU basis.

Change CPU time statistics (cputime) to be accounted on a per-CPU basis.

	(a) remove struct cp_time, it was redundant since kinfo_cputime has
	    been introduced; kinfo_get_sched_cputime(3) function makes use
	    of the latter struct.

	(b) change global definition from cp_time into cpu_time, it's now a
	    #define that hides the ugliness of percpu array indexing.

	(c) minor style(9) cleanups in nearby code.

Reviewed-by/discussed-with: Matthew Dillon <dillon@backplane.com>