mb/google/poppy/variants: Set pch_trip_temp to 75C

Similar to Soraka, this change sets the pch_trip_temp value to
75C. This is important so that PMC can shutdown the thermal sensor
when CPU is in C-state and DTS temp <= pch_trip_temp.

BUG=b:74089135

Change-Id: Ic46fa0681796b821dfb014ab91734c960df7846a
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/24968
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/mainboard/google/poppy/variants/baseboard/devicetree.cb

@@ -264,6 +264,9 @@ chip soc/intel/skylake
 	# Lock Down
 	register "chipset_lockdown" = "CHIPSET_LOCKDOWN_COREBOOT"
 
+	# PCH Trip Temperature in degree C
+	register "pch_trip_temp" = "75"
+
 	device cpu_cluster 0 on
 		device lapic 0 on end
 	end

src/mainboard/google/poppy/variants/nami/devicetree.cb

@@ -234,6 +234,9 @@ chip soc/intel/skylake
 	# Lock Down
 	register "chipset_lockdown" = "CHIPSET_LOCKDOWN_COREBOOT"
 
+	# PCH Trip Temperature in degree C
+	register "pch_trip_temp" = "75"
+
 	device cpu_cluster 0 on
 		device lapic 0 on end
 	end

src/mainboard/google/poppy/variants/nautilus/devicetree.cb

@@ -282,6 +282,9 @@ chip soc/intel/skylake
 	# Lock Down
 	register "chipset_lockdown" = "CHIPSET_LOCKDOWN_COREBOOT"
 
+	# PCH Trip Temperature in degree C
+	register "pch_trip_temp" = "75"
+
 	device cpu_cluster 0 on
 		device lapic 0 on end
 	end