x86: cros_ec: Enable cros_ec for link

Add defines to enable the Chrome OS EC interface and set it up on init.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/chromebook-x86/coreboot/Makefile b/board/chromebook-x86/coreboot/Makefile
index 4f2ac89..27ebe78 100644
--- a/board/chromebook-x86/coreboot/Makefile
+++ b/board/chromebook-x86/coreboot/Makefile
@@ -12,4 +12,4 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-obj-y	+= coreboot_start.o
+obj-y	+= coreboot_start.o coreboot.o