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/sandbox_defconfig b/configs/sandbox_defconfig
index 0bf5ea3..70f5b86 100644
--- a/configs/sandbox_defconfig
+++ b/configs/sandbox_defconfig
@@ -7,3 +7,8 @@
 CONFIG_DEFAULT_DEVICE_TREE="sandbox"
 CONFIG_SYS_MALLOC_F=y
 CONFIG_SYS_MALLOC_F_LEN=0x400
+CONFIG_CROS_EC=y
+CONFIG_DM_CROS_EC=y
+CONFIG_CROS_EC_SANDBOX=y
+CONFIG_CROS_EC_KEYB=y
+CONFIG_CMD_CROS_EC=y