thermal: ti-soc-thermal: Enable addition power management

The bandgap sensor can be idled when the processor is too, but it
isn't currently being done, so the power consumption of OMAP3
boards can elevated if the bangap sensor is enabled.

This patch attempts to use some additional power management
to idle the clock to the bandgap when not needed.

Signed-off-by: Adam Ford <aford173@gmail.com>
Reported-by: kernel test robot <lkp@intel.com>
Tested-by: Andreas Kemnade <andreas@kemnade.info> # GTA04
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200911123157.759379-1-aford173@gmail.com