dm: cros_ec: Convert to Kconfig

Since both I2C and SPI are converted to Kconfig, we can convert cros_ec
to Kconfig for these buses.

LPC will need to wait until driver mode PCI is available.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/snow_defconfig b/configs/snow_defconfig
index 14ed793..353ddb0 100644
--- a/configs/snow_defconfig
+++ b/configs/snow_defconfig
@@ -3,3 +3,8 @@
 +S:CONFIG_ARCH_EXYNOS=y
 +S:CONFIG_TARGET_SNOW=y
 CONFIG_DEFAULT_DEVICE_TREE="exynos5250-snow"
+CONFIG_CROS_EC=y
+CONFIG_DM_CROS_EC=y
+CONFIG_CROS_EC_I2C=y
+CONFIG_CROS_EC_KEYB=y
+CONFIG_CMD_CROS_EC=y