clk: mxs: get base address from device tree

Instead of using the static definitions, get clkctrl and digctl base
addresses with mapping from device tree.

Use macro on variable is not nice, but it's done here to save huge
pointless diff stat.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Mike Turquette <mturquette@linaro.org>
diff --git a/arch/arm/boot/dts/imx28.dtsi b/arch/arm/boot/dts/imx28.dtsi
index c2f10d3..d306ff5 100644
--- a/arch/arm/boot/dts/imx28.dtsi
+++ b/arch/arm/boot/dts/imx28.dtsi
@@ -647,6 +647,7 @@
 			};
 
 			digctl@8001c000 {
+				compatible = "fsl,imx28-digctl";
 				reg = <0x8001c000 0x2000>;
 				interrupts = <89>;
 				status = "disabled";