mb/google/volteer: Enable RP LTR setting

BUG=b:151166040
TEST= build and boot volteer and check LTR and AER value
from FSP log

Signed-off-by: Wonkyu Kim <wonkyu.kim@intel.com>
Change-Id: Ibbf55e6a08ff5e8f358325bb8e9f1487cc982f95
Reviewed-on: https://review.coreboot.org/c/coreboot/+/40268
Reviewed-by: Nick Vaccaro <nvaccaro@google.com>
Reviewed-by: Srinidhi N Kaushik <srinidhi.n.kaushik@intel.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/mainboard/google/volteer/variants/baseboard/devicetree.cb b/src/mainboard/google/volteer/variants/baseboard/devicetree.cb
index 361e563..ab911d2 100644
--- a/src/mainboard/google/volteer/variants/baseboard/devicetree.cb
+++ b/src/mainboard/google/volteer/variants/baseboard/devicetree.cb
@@ -43,20 +43,24 @@
 
 	# Enable NVMe PCIE 9 using clk 0
 	register "PcieRpEnable[8]" = "1"
+	register "PcieRpLtrEnable[8]" = "1"
 	register "PcieClkSrcUsage[0]" = "8"
 	register "PcieClkSrcClkReq[0]" = "0"
 
 	# Enable Optane PCIE 11 using clk 0
 	register "PcieRpEnable[10]" = "1"
+	register "PcieRpLtrEnable[10]" = "1"
 	register "HybridStorageMode" = "1"
 
 	# Enable SD Card PCIE 8 using clk 3
 	register "PcieRpEnable[7]" = "1"
+	register "PcieRpLtrEnable[7]" = "1"
 	register "PcieClkSrcUsage[3]" = "7"
 	register "PcieClkSrcClkReq[3]" = "3"
 
 	# Enable WLAN PCIE 7 using clk 1
 	register "PcieRpEnable[6]" = "1"
+	register "PcieRpLtrEnable[6]" = "1"
 	register "PcieClkSrcUsage[1]" = "6"
 	register "PcieClkSrcClkReq[1]" = "1"