mb/intel/tglrvp : Enable RP LTR

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: I8ab7667d788563ffcb9287a64254590ef9bea5d8
Reviewed-on: https://review.coreboot.org/c/coreboot/+/40269
Reviewed-by: Srinidhi N Kaushik <srinidhi.n.kaushik@intel.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/mainboard/intel/tglrvp/variants/tglrvp_up3/devicetree.cb b/src/mainboard/intel/tglrvp/variants/tglrvp_up3/devicetree.cb
index 501aa2a..82303c6 100644
--- a/src/mainboard/intel/tglrvp/variants/tglrvp_up3/devicetree.cb
+++ b/src/mainboard/intel/tglrvp/variants/tglrvp_up3/devicetree.cb
@@ -45,6 +45,12 @@
 	register "PcieRpEnable[8]" = "1"
 	register "PcieRpEnable[10]" = "1"
 
+	# Enable RP LTR
+	register "PcieRpLtrEnable[2]" = "1"
+	register "PcieRpLtrEnable[3]" = "1"
+	register "PcieRpLtrEnable[8]" = "1"
+	register "PcieRpLtrEnable[10]" = "1"
+
 	# Hybrid storage mode
 	register "HybridStorageMode" = "1"