subsys_initcall causes problems registering the driver as a thermal
cooling device.

If "faster boot" is the main reason for doing subsys_initcall, this
should be handled in the bootloader or another boot constraint
framework.
Signed-off-by: Amit Kucheria <amit.kucheria@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>