google/chromeec: Add ACPI method for EC Panic

Add an ACPI method to handle EC_HOST_EVENT_PANIC (bit 24) events.

EC panic is not covered by the standard (0-F) ACPI notify values.
Arbitrarily choosing B0 notify, which is in the 84-BF device specific
ACPI notify range.

This will be a no-op until the kernel driver is also updated to handle
this event.

BUG=b:258195448
BRANCH=None
TEST=Observe event with modified cros_ec_lpc driver

Signed-off-by: Rob Barnes <robbarnes@google.com>
Change-Id: Iafa642c1c50f9a0083a8e618e1eabec9a7ce39b4
Reviewed-on: https://review.coreboot.org/c/coreboot/+/69391
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/ec/google/chromeec/acpi/ec.asl

@@ -12,6 +12,8 @@
 #define EC_OEM_VARIABLE_DATA_MASK	0x7
 #define INT3400_ODVP_CHANGED		0x88
 
+#define ACPI_NOTIFY_CROS_EC_PANIC	0xB0
+
 // Mainboard specific throttle handler
 #ifdef DPTF_ENABLE_CHARGER
 External (\_SB.DPTF.TCHG, DeviceObj)
@@ -409,6 +411,13 @@ Device (EC0)
 		\PNOT ()
 	}
 
+	// EC Panic
+	Method (_Q18, 0, NotSerialized)
+	{
+		Printf ("EC: PANIC")
+		Notify (CREC, ACPI_NOTIFY_CROS_EC_PANIC)
+	}
+
 	// MKBP interrupt.
 	Method (_Q1B, 0, NotSerialized)
 	{