tools/power turbostat: update --list feature

Make it possible to take the entire un-edited output
from `turbostat --list` and feed it to "turbostat --show"
or "turbostat --hide".

To do this, the leading comma was removed
(no mater what columns are active)
and also they dynamic C-state "C1, C2, C3" etc are replaced
by the string "sysfs", which refers to them as a group.

Signed-off-by: Len Brown <len.brown@intel.com>