drivers: bus: add a new driver for WEIM

The WEIM(Wireless External Interface Module) works like a bus.
You can attach many different devices on it, such as NOR, onenand.

In the case of i.MX6q-sabreauto, the NOR is connected to WEIM.

This patch also adds the devicetree binding document.
The driver only works when the devicetree is enabled.

Signed-off-by: Huang Shijie <b32955@freescale.com>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
diff --git a/drivers/bus/Kconfig b/drivers/bus/Kconfig
index b05ecab..46cd5bb 100644
--- a/drivers/bus/Kconfig
+++ b/drivers/bus/Kconfig
@@ -4,6 +4,15 @@
 
 menu "Bus devices"
 
+config IMX_WEIM
+	bool "Freescale EIM DRIVER"
+	depends on ARCH_MXC
+	help
+	  Driver for i.MX6 WEIM controller.
+	  The WEIM(Wireless External Interface Module) works like a bus.
+	  You can attach many different devices on it, such as NOR, onenand.
+	  But now, we only support the Parallel NOR.
+
 config MVEBU_MBUS
 	bool
 	depends on PLAT_ORION