mb/google/volteer: configure L1Substate for PCIe

Limit PcieL1Substate for RP9, RP11 for ES1 NVMe warm reboot workaround.

Reference: #613582 Tiger Lake PCH-LP Sightings Report
           issue id #1409566330

BUG=none
BRANCH=none
TEST= boot to OS and check warm reboot with NVMe

Signed-off-by: Wonkyu Kim <wonkyu.kim@intel.com>
Change-Id: Ie85bf71c43427e326ef2ba674da4566f8f51495a
Reviewed-on: https://review.coreboot.org/c/coreboot/+/39413
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Srinidhi N Kaushik <srinidhi.n.kaushik@intel.com>
Reviewed-by: Nick Vaccaro <nvaccaro@google.com>

src/mainboard/google/volteer/variants/ripto/overridetree.cb

@@ -1,5 +1,10 @@
 chip soc/intel/tigerlake
 
+	# NVMe warm reboot workaround
+	# Limit L1.1 (value:2) for RP9, RP11
+	register "PcieRpL1Substates[8]" = "2"
+	register "PcieRpL1Substates[10]" = "2"
+
 	device domain 0 on
 	end