ARM: imx: create mxc_arch_reset_init_dt() for DT boot

The mxc_arch_reset_init() uses static mapping and calls clk_get_sys() to
get clock.  It's suitable for non-DT boot but not for DT boot where
dynamic mapping and of_clk_get() should be used instead.  Create
mxc_arch_reset_init_dt() as the DT variant of mxc_arch_reset_init(),
and change DT platforms to use it.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
diff --git a/arch/arm/mach-imx/system.c b/arch/arm/mach-imx/system.c
index 02cf449..7cdc79a 100644
--- a/arch/arm/mach-imx/system.c
+++ b/arch/arm/mach-imx/system.c
@@ -21,6 +21,8 @@
 #include <linux/io.h>
 #include <linux/err.h>
 #include <linux/delay.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
 
 #include <asm/system_misc.h>
 #include <asm/proc-fns.h>
@@ -75,3 +77,21 @@
 
 	clk_prepare(wdog_clk);
 }
+
+void __init mxc_arch_reset_init_dt(void)
+{
+	struct device_node *np;
+
+	np = of_find_compatible_node(NULL, NULL, "fsl,imx21-wdt");
+	wdog_base = of_iomap(np, 0);
+	WARN_ON(!wdog_base);
+
+	wdog_clk = of_clk_get(np, 0);
+	if (IS_ERR(wdog_clk)) {
+		pr_warn("%s: failed to get wdog clock\n", __func__);
+		wdog_clk = NULL;
+		return;
+	}
+
+	clk_prepare(wdog_clk);
+}