Add 20 intel_pstate and cpufreq scaling driver cases

Signed-off-by: qwang59 <[email protected]>

pstate/README.md

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+# Release Notes for Intel Pstate cases
+
+The cpufreq driver is a generic CPU frequency scaling driver that provides a framework 
+for managing the CPU frequency, while Intel_Pstate driver is a specific CPU frequency
+for Intel® Architecture-based processors. These drivers are specifically optimized for 
+Intel_pstate and rely on the cpufreq sysfs attributes for configuration.
+
+The tests file contains the cases that are applicable to both Intel® client and Server platforms.
+At present, the tests do not cover non-HWP mode, but are exclusively designed for Hardware P-state mode.
+HWP stands for Hardware-controlled Performance States, For more information on the HWP specifiction, 
+please consult the Intel® Software Developer's Manual.
+
+You can run the cases one by one, e.g. command
+
+```
+./intel_pstate_tests.sh -t verify_sysfs_atts
+```
+You also can run the cases together with runtests command, e.g.
+
+```
+cd ..
+./runtests -f pstate/tests -o logfile
+```
+
+These are the basic cases for CPU pstates, If you have good idea to 
+improve pstate cases, you are welcomed to send us the patches, thanks!