mb/google/skyrim/var/frostflow: Add non-ChromeOS TBMC support

The TBMC ACPI device is used by Windows ChromeEC drivers to determine
tablet mode and to enable motion sensors (accelerometer, gyroscope).
Since it's not needed/used by ChromeOS, restrict its inclusion to
non-ChromeOS builds.

TEST=build/boot Win11/Linux on frostflow, verify tablet mode and
rotation work properly, keyboard/touchpad disabled in tablet mode.

Change-Id: Iedc68797776d43f37dd97e5251cf9b9a016f1bd5
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/91800
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin L Roth <gaumless@gmail.com>

src/mainboard/google/skyrim/variants/frostflow/include/variant/ec.h

@@ -1,3 +1,13 @@
 /* SPDX-License-Identifier: GPL-2.0-or-later */
 
+#ifndef __VARIANT_EC_H__
+#define __VARIANT_EC_H__
+
 #include <baseboard/ec.h>
+
+/* Enable Tablet switch for Windows drivers */
+#if !CONFIG(CHROMEOS)
+#define EC_ENABLE_TBMC_DEVICE
+#endif
+
+#endif