ARM i.MX dtsi: Add default bus-width property for esdhc controller

According to Documentation/devicetree/bindings/mmc/mmc.txt bus-width
is a mandatory property. While this is currently enforced nowhere, it's
a good habit to just add the property now to allow to add common helper
functionality for the mmc property parsing later.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
diff --git a/arch/arm/boot/dts/imx51.dtsi b/arch/arm/boot/dts/imx51.dtsi
index 54aea74..0bc8ae7 100644
--- a/arch/arm/boot/dts/imx51.dtsi
+++ b/arch/arm/boot/dts/imx51.dtsi
@@ -87,6 +87,7 @@
 					compatible = "fsl,imx51-esdhc";
 					reg = <0x70008000 0x4000>;
 					interrupts = <2>;
+					bus-width = <4>;
 					status = "disabled";
 				};
 
@@ -119,6 +120,7 @@
 					compatible = "fsl,imx51-esdhc";
 					reg = <0x70020000 0x4000>;
 					interrupts = <3>;
+					bus-width = <4>;
 					status = "disabled";
 				};
 
@@ -126,6 +128,7 @@
 					compatible = "fsl,imx51-esdhc";
 					reg = <0x70024000 0x4000>;
 					interrupts = <4>;
+					bus-width = <4>;
 					status = "disabled";
 				};
 			};