event: Convert arch_cpu_init_dm() to use events

Instead of a special function, send an event after driver model is inited
and adjust the boards which use this function.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/mach-imx/imx8/cpu.c b/arch/arm/mach-imx/imx8/cpu.c
index ee5cc47..359f8c7 100644
--- a/arch/arm/mach-imx/imx8/cpu.c
+++ b/arch/arm/mach-imx/imx8/cpu.c
@@ -8,6 +8,7 @@
 #include <cpu.h>
 #include <cpu_func.h>
 #include <dm.h>
+#include <event.h>
 #include <init.h>
 #include <log.h>
 #include <asm/cache.h>
@@ -66,7 +67,7 @@
 	return 0;
 }
 
-int arch_cpu_init_dm(void)
+static int imx8_init_mu(void *ctx, struct event *event)
 {
 	struct udevice *devp;
 	int node, ret;
@@ -88,6 +89,7 @@
 
 	return 0;
 }
+EVENT_SPY(EVT_DM_POST_INIT, imx8_init_mu);
 
 int print_bootinfo(void)
 {