mmc: sdhci-spear: add device tree bindings

This adds simple DT bindings for SDHCI SPEAr controller. It uses cd-gpios
from common mmc bindings.

This also fixes spear300-evb.dts with correct name for card detect binding.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Chris Ball <cjb@laptop.org>
diff --git a/arch/arm/boot/dts/spear300-evb.dts b/arch/arm/boot/dts/spear300-evb.dts
index d71b8d5..1e7c7a8 100644
--- a/arch/arm/boot/dts/spear300-evb.dts
+++ b/arch/arm/boot/dts/spear300-evb.dts
@@ -80,8 +80,7 @@
 		};
 
 		sdhci@70000000 {
-			int-gpio = <&gpio1 0 0>;
-			power-gpio = <&gpio1 2 1>;
+			cd-gpios = <&gpio1 0 0>;
 			status = "okay";
 		};