mb/google/myst: Add smihandler

Add SMI handler code for Myst platform.

BUG=b:275858191
TEST=builds

Signed-off-by: Jon Murphy <jpmurphy@google.com>
Change-Id: I92e5e6aef7ab0b84a96d976e29ebf96b56f6f1a1
Reviewed-on: https://review.coreboot.org/c/coreboot/+/74100
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>

src/mainboard/google/myst/variants/baseboard/Makefile.inc

@@ -1,3 +1,5 @@
 bootblock-y += gpio.c
 
 ramstage-y += gpio.c
+
+smm-y += smihandler.c

src/mainboard/google/myst/variants/baseboard/smihandler.c

@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include <baseboard/variants.h>
+#include <cpu/x86/smm.h>
+#include <ec/google/chromeec/ec.h>
+#include <ec/google/chromeec/smm.h>
+#include <variant/ec.h>
+
+void mainboard_smi_sleep(u8 slp_typ)
+{
+	chromeec_smi_sleep(slp_typ, MAINBOARD_EC_S0IX_WAKE_EVENTS, MAINBOARD_EC_S5_WAKE_EVENTS);
+}
+
+int mainboard_smi_apmc(u8 apmc)
+{
+	chromeec_smi_apmc(apmc, MAINBOARD_EC_SCI_EVENTS, MAINBOARD_EC_SMI_EVENTS);
+
+	return 0;
+}