Kernel: Report more accurate ticks per second for APIC timer

Author: https://github.com/tomuta
Commit: 180cc85d79
Pull-request: https://github.com/SerenityOS/serenity/pull/3872

Kernel/Time/APICTimer.cpp

@@ -128,6 +128,9 @@ bool APICTimer::calibrate(HardwareTimerBase& calibration_source)
     }
 #endif
 
+    // TODO: measure rather than assuming it matches?
+    m_frequency = calibration_source.ticks_per_second();
+
     enable_local_timer();
     return true;
 }