With gen < 9 we have had always 50Mhz units as our hw
ratio. With gen >= 9 the hw ratio changed to 16.667Mhz (50/3).
The result was that our gpu frequency tracing started to output
values 3 times larger than expected due to hardcoded scaling
value. Fix this by using Use intel_gpu_freq() when generating Mhz
value from ratio for 'intel_gpu_freq_change' trace event.