tools/power/x86/amd_pstate_tracer: Fix python gnuplot package names

The prerequisites section listed non-existent packages
"phython-gnuplot" and "phython3-gnuplot", which may mislead users and
cause installation failures.

Update the names to the correct distribution package names
"python-gnuplot" and "python3-gnuplot", helping users avoid confusion
and saving time for those following the instructions.

Signed-off-by: Kuan-Wei Chiu <[e-mail]>
Reviewed-by: Mario Limonciello <[e-mail]>
Signed-off-by: Mario Limonciello (AMD) <[e-mail]>

tools/power/x86/amd_pstate_tracer/amd_pstate_trace.py

···
     gnuplot 5.0 or higher
     gnuplot-py 1.8 or higher
     (Most of the distributions have these required packages. They may be called
-     gnuplot-py, phython-gnuplot or phython3-gnuplot, gnuplot-nox, ... )
+     gnuplot-py, python-gnuplot or python3-gnuplot, gnuplot-nox, ... )
 
     Kernel config for Linux trace is enabled