#114 Thinkpad X200 T9550@2.66GHz CPU frequency support

Hi, I'm librebooting my Thinkpad X200 with Core 2 Duo T9550 CPU. The CPU is pretty rare on X200 models. When using the 20210522 or 20211122 firmware, the CPU frequency is locked at 1.6 GHz. `tlp-stat -p` output shows that all CPU-related drivers are not supported, and dmesg log shows this: `intel_pstate: CPU model not supported`. I tried both grub and seabios payload firmware. When using 20160907 stable firmware, everything about CPU frequency works fine and, for example, I can use ondemand governer to let CPU frequency change according to workload, and tlp reports available frequencies and governors correctly. I really hope I could use the new version of libreboot because the idle power consumption is much better and there's no CCFL screen coil whine(in 20160907 firmware, coil whine only disappears at maximum screen brightness), but the CPU problem is holding me back.