selftests: amd-pstate: Split basic.sh into run.sh and basic.sh.

Split basic.sh into run.sh and basic.sh.
The modification makes basic.sh more pure, just for test basic kernel
functions. The file of run.sh mainly contains functions such as test
entry, parameter check, prerequisite and log clearing etc.
Then you can specify test case in kselftest/amd-pstate, for example:
sudo ./run.sh -c basic. The detail please run the below script.
./run.sh --help

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>