dm: exynos: cros_ec: Move cros_ec_spi to driver model

Adjust this driver to use driver model and move smdk5420 boards over to
use it.

Acked-by: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/configs/peach-pit.h b/include/configs/peach-pit.h
index ab8ac60..91bd37d 100644
--- a/include/configs/peach-pit.h
+++ b/include/configs/peach-pit.h
@@ -38,6 +38,7 @@
 
 #define CONFIG_POWER_TPS65090_EC
 #define CONFIG_CROS_EC_SPI		/* Support CROS_EC over SPI */
+#define CONFIG_DM_CROS_EC
 
 #define CONFIG_USB_XHCI
 #define CONFIG_USB_XHCI_EXYNOS