mb/system76: Enable S0ix for darp8/darp9

The newer batch of these boards do not de-assert VW PLTRST# on S3
resume, causes the units to not power on in the EC code. Switch them to
S0ix by default, but leave S3 available.

Change-Id: I95337c1391102db9e020e82bdd938659c1a4f905
Signed-off-by: Tim Crawford <tcrawford@system76.com>

Author: crawfxrd

src/mainboard/system76/adl/variants/darp8/overridetree.cb

@@ -1,6 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0-only
 
 chip soc/intel/alderlake
+	register "s0ix_enable" = "1"
+
 	register "power_limits_config[ADL_P_282_442_482_28W_CORE]" = "{
 		.tdp_pl1_override = 20,
 		.tdp_pl2_override = 56,

src/mainboard/system76/rpl/variants/darp9/overridetree.cb

@@ -1,6 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0-only
 
 chip soc/intel/alderlake
+	register "s0ix_enable" = "1"
+
 	register "power_limits_config[RPL_P_682_482_282_28W_CORE]" = "{
 		.tdp_pl1_override = 20,
 		.tdp_pl2_override = 56,