ARM: mxs: look up timrot clock from device tree

Change call clk_get_sys() to of_clk_get() to look up timrot clock from
device tree, so that the clk_register_clkdev() call for timrot can be
saved in clock driver.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
diff --git a/arch/arm/boot/dts/imx23.dtsi b/arch/arm/boot/dts/imx23.dtsi
index 56afcf4..27ce807 100644
--- a/arch/arm/boot/dts/imx23.dtsi
+++ b/arch/arm/boot/dts/imx23.dtsi
@@ -426,6 +426,7 @@
 				compatible = "fsl,imx23-timrot", "fsl,timrot";
 				reg = <0x80068000 0x2000>;
 				interrupts = <28 29 30 31>;
+				clocks = <&clks 28>;
 			};
 
 			auart0: serial@8006c000 {
diff --git a/arch/arm/boot/dts/imx28.dtsi b/arch/arm/boot/dts/imx28.dtsi
index 7ba4966..c2f10d3 100644
--- a/arch/arm/boot/dts/imx28.dtsi
+++ b/arch/arm/boot/dts/imx28.dtsi
@@ -838,6 +838,7 @@
 				compatible = "fsl,imx28-timrot", "fsl,timrot";
 				reg = <0x80068000 0x2000>;
 				interrupts = <48 49 50 51>;
+				clocks = <&clks 26>;
 			};
 
 			auart0: serial@8006a000 {
diff --git a/arch/arm/mach-mxs/timer.c b/arch/arm/mach-mxs/timer.c
index fe2903d..f5142aa 100644
--- a/arch/arm/mach-mxs/timer.c
+++ b/arch/arm/mach-mxs/timer.c
@@ -247,7 +247,7 @@
 	struct clk *timer_clk;
 	int irq;
 
-	timer_clk = clk_get_sys("timrot", NULL);
+	timer_clk = of_clk_get(np, 0);
 	if (IS_ERR(timer_clk)) {
 		pr_err("%s: failed to get clk\n", __func__);
 		return;