thermal: imx: correct driver load sequence for cpu cooling

thermal driver should be regisetered after cpufreq driver has
been registered and probed. Doing so is to make sure that thermal
driver can get the max cpu cooling states correctly when calling
get_property.

Signed-off-by: Bai Ping <b51503@freescale.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>