cros_ec: Move cros_ec_dev module to drivers/mfd

The cros_ec_dev module is responsible for registering the MFD devices
attached to the ChromeOS EC. This patch moves this module to drivers/mfd
so calls to mfd_add_devices() are not done from outside the MFD subtree
anymore.

Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Reviewed-by: Gwendal Grignou <gwendal@chromium.org>
Tested-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 1d20a80..538a2ae 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -222,6 +222,16 @@
 	  response time cannot be guaranteed, we support ignoring
 	  'pre-amble' bytes before the response actually starts.
 
+config MFD_CROS_EC_CHARDEV
+        tristate "Chrome OS Embedded Controller userspace device interface"
+        depends on MFD_CROS_EC
+        select CROS_EC_CTL
+        ---help---
+          This driver adds support to talk with the ChromeOS EC from userspace.
+
+          If you have a supported Chromebook, choose Y or M here.
+          The module will be called cros_ec_dev.
+
 config MFD_ASIC3
 	bool "Compaq ASIC3"
 	depends on GPIOLIB && ARM