mmc: sdhci-spear: Add clk_{un}prepare() support

clk_{un}prepare is mandatory for platforms using common clock framework.
Since this driver is used by SPEAr platform, which supports common clock
framework, add clk_{un}prepare() support for it.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Chris Ball <cjb@laptop.org>

Documentation/devicetree/bindings/mmc/sdhci-spear.txt

@@ -9,13 +9,10 @@ Required properties:
 Optional properties:
 - cd-gpios: card detect gpio, with zero flags.
 
-If your board don't support these gpios then don't pass the entry.
-
 Example:
 
 	sdhci@fc000000 {
 		compatible = "st,spear300-sdhci";
 		reg = <0xfc000000 0x1000>;
-
-		cd-gpios = <&gpio0 6 0>
+		cd-gpios = <&gpio0 6 0>;
 	};