staging: omap-thermal: common code to expose driver to thermal framework

This patch has the common thermal framework support for OMAP
bandgap driver. It includes the zone registration and unregistration,
the cpu cooling and the trip definitions.

The trips definition is essentially one trip for passive cooling
using the generic cpu cooling device and another one for thermal
shutdown. The cpu cooling device is built based on the existing
cpu freq table. The build should be agnostic to omap version,
but relies that cpufreq is up and running by the time the driver
registers the cpu cooling, as it relies on the table walk api
from cpufreq.

Signed-off-by: Eduardo Valentin <eduardo.valentin@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>