x86/APIC: no need for timer calibration when using TDT

x86/APIC: no need for timer calibration when using TDT

The only global effect of calibrate_APIC_clock() is the setting of
"bus_scale"; the final __setup_APIC_LVTT(0) is (at best) redundant with
the immediately following setup_APIC_timer() invocation. Yet "bus_scale"
isn't used when using TDT. Avoid wasting 100ms for calibration in this
case.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>