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/Kconfig b/arch/Kconfig
index e619144..1b35fda 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -94,6 +94,7 @@
 	bool "Nios II architecture"
 	select CPU
 	select DM
+	imply DM_EVENT
 	select OF_CONTROL
 	select SUPPORT_OF_CONTROL
 	imply CMD_DM
@@ -113,6 +114,7 @@
 	select DM
 	imply DM_SERIAL
 	imply DM_ETH
+	imply DM_EVENT
 	imply DM_MMC
 	imply DM_SPI
 	imply DM_SPI_FLASH
@@ -238,6 +240,7 @@
 	imply CMD_SF_TEST
 	imply CMD_ZBOOT
 	imply DM_ETH
+	imply DM_EVENT
 	imply DM_GPIO
 	imply DM_KEYBOARD
 	imply DM_MMC