x86: Defer LAPIC calibration until after timecounters are available

x86: Defer LAPIC calibration until after timecounters are available

This ensures that we have a good reference timecounter for performing
calibration.

Change lapic_setup to avoid configuring the timer when booting, and move
calibration and initial configuration to a new lapic routine,
lapic_calibrate_timer.  This calibration will be initiated from
cpu_initclocks(), before an eventtimer is selected.

Reviewed by:	kib, jhb
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D33206