PM / devfreq: event: support rockchip dfi controller

on rk3399 platform, there is dfi conroller can monitor
ddr load, base on this result, we can do ddr freqency
scaling.

Signed-off-by: Lin Huang <hl@rock-chips.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Acked-by: Chanwoo Choi <cw00.choi@samsung.com>
diff --git a/drivers/devfreq/event/Kconfig b/drivers/devfreq/event/Kconfig
index 1d1cd78..0fdae86 100644
--- a/drivers/devfreq/event/Kconfig
+++ b/drivers/devfreq/event/Kconfig
@@ -30,4 +30,11 @@
 	  (Platform Performance Monitoring Unit) counters to estimate the
 	  utilization of each module.
 
+config DEVFREQ_EVENT_ROCKCHIP_DFI
+	tristate "ROCKCHIP DFI DEVFREQ event Driver"
+	depends on ARCH_ROCKCHIP
+	help
+	  This add the devfreq-event driver for Rockchip SoC. It provides DFI
+	  (DDR Monitor Module) driver to count ddr load.
+
 endif # PM_DEVFREQ_EVENT