cpupower: Move needs_root variable into a sub-struct

Move the needs_root variable into a sub-struct. This is in preparation
for adding a new flag for cpuidle_monitor.

Update all uses of the needs_root variable to reflect this change.

Signed-off-by: Janakarajan Natarajan <Janakarajan.Natarajan@amd.com>
Acked-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>