mainboards,ec: provide common declaration for mainboard_ec_init()

Add a header file to provide common declarations that the
mainboards can use regarding EC init.

BUG=chrome-os-partner:56677

Change-Id: Iaa0b37eff4de644e969a18364713b90b7f27fa1c
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/16734
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
Tested-by: build bot (Jenkins)
diff --git a/src/mainboard/intel/kunimitsu/ec.h b/src/mainboard/intel/kunimitsu/ec.h
index 15d8e6d..ba9a450 100644
--- a/src/mainboard/intel/kunimitsu/ec.h
+++ b/src/mainboard/intel/kunimitsu/ec.h
@@ -17,6 +17,7 @@
 #ifndef MAINBOARD_EC_H
 #define MAINBOARD_EC_H
 
+#include <ec/ec.h>
 #include <ec/google/chromeec/ec_commands.h>
 
 #define MAINBOARD_EC_SCI_EVENTS \
@@ -55,8 +56,4 @@
 	 EC_HOST_EVENT_MASK(EC_HOST_EVENT_BATTERY_SHUTDOWN)|\
 	 EC_HOST_EVENT_MASK(EC_HOST_EVENT_PANIC))
 
-#ifndef __ACPI__
-extern void mainboard_ec_init(void);
-#endif
-
 #endif