thermal: remove stale THERMAL_POWER_ACTOR select

A previous version of this patch had a config for THERMAL_POWER_ACTOR
but it was dropped.  Remove the select as it is not doing anything.

Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Eduardo Valentin <edubezval@gmail.com>
Reported-by: Valentin Rothberg <valentinrothberg@gmail.com>
Signed-off-by: Javi Merino <javi.merino@arm.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

diff --cc drivers/thermal/Kconfig
Simple merge