ec/starlabs/merlin: Change RPTS method to Serialized

Signed-off-by: Sean Rhodes <sean@starlabs.systems>
Change-Id: Id64d321846dc042d4092d39ce9598d028ab15ed0
Reviewed-on: https://review.coreboot.org/c/coreboot/+/62417
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Andy Pont <andy.pont@sdcsystems.com>
Reviewed-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>

src/ec/starlabs/merlin/acpi/suspend.asl

@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
-Method (RPTS, 1, NotSerialized)
+Method (RPTS, 1, Serialized)
 {
 	If ((Arg0 == 0x04) || (Arg0 == 0x05))
 	{