selftests: amd-pstate: Trigger gitsource benchmark and test cpus

Add gitsource.sh trigger the gitsource testing and monitor the cpu desire
performance, frequency, load, power consumption and throughput etc.
1) Download and tar gitsource codes.
2) Run gitsource benchmark on specific governors, ondemand or schedutil.
3) Run tbench benchmark comparative test on acpi-cpufreq kernel driver.
4) Get desire performance, frequency, load by perf.
5) Get power consumption and throughput by amd_pstate_trace.py.
6) Get run time by /usr/bin/time.
7) Analyse test results and save it in file selftest.gitsource.csv.
8) Plot png images about time, energy and performance per watt
for each test.

Fixed whitespace error during commit:
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Signed-off-by: Meng Li <li.meng@amd.com>
Acked-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>