x86: Do not attempt to calibrate the LAPIC timer if no APIC is present

Reported and tested by: Michael Butler <imb@protected-networks.net>
Reviewed by: jhb, kib
Fixes: 62d09b46ad75 ("x86: Defer LAPIC calibration until after timecounters are available")
MFC after: 3 days
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D33669