Thermal: Introduce a step_wise thermal governor

This patch adds a simple step_wise governor to the
generic thermal layer. This algorithm throttles the
cooling devices in a linear fashion. If the 'trend'
is heating, it throttles by one step. And if the
thermal trend is cooling it de-throttles by one step.

This actually moves the throttling logic from thermal_sys.c
and puts inside step_wise.c, without any change.

Signed-off-by: Durgadoss R <durgadoss.r@intel.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
index 84b0f03..7e1b6de 100644
--- a/drivers/thermal/Kconfig
+++ b/drivers/thermal/Kconfig
@@ -61,3 +61,9 @@
 	depends on THERMAL
 	help
 	  Enable this to manage platform thermals using fair-share governor.
+
+config STEP_WISE
+	bool "Step_wise thermal governor"
+	depends on THERMAL
+	help
+	  Enable this to manage platform thermals using a simple linear