apic: prevent divide by zero in CPU frequency init

If a CPU for some reason returns 0 as CPU frequency, we currently panic
on the resulting divide by zero when trying to initialize the CPU(s) via
APIC. When this happens, we'll fallback to measuring the frequency
instead.

PR: 269767
Reviewed by: imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/664

sys/x86/x86/local_apic.c

@@ -953,7 +953,7 @@ lapic_calibrate_initcount_cpuid_vm(void)
 
 	/* Record divided frequency. */
 	count_freq = freq / lapic_timer_divisor;
-	return (true);
+	return (count_freq != 0);
 }
 
 static uint64_t