ivy: Add a possiblity for mainboard early init.

This is needed for stout EC init.

Change-Id: I5c73499c17763229840152a473a2d820802ee2f6
Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-on: https://review.coreboot.org/13535
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>
diff --git a/src/mainboard/lenovo/t420s/romstage.c b/src/mainboard/lenovo/t420s/romstage.c
index 1080e1c..c020458 100644
--- a/src/mainboard/lenovo/t420s/romstage.c
+++ b/src/mainboard/lenovo/t420s/romstage.c
@@ -67,3 +67,6 @@
 	read_spd(&spd[0], 0x50);
 	read_spd(&spd[2], 0x51);
 }
+
+void mainboard_early_init(int s3resume) {
+}