soc/amd/picasso: add devicetree setting for PSPP policy

Since the default for the corresponding UPD of the Picasso FSP is
DXIO_PSPP_POWERSAVE and the devicetree default is DXIO_PSPP_PERFORMANCE,
add a deviectree setting for each board that's using the Picasso SoC
code to not change the setting for the existing boards.

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Change-Id: I0008ebb0c0f339ed3bdf24ab95a20aa83d5be2c9
Reviewed-on: https://review.coreboot.org/c/coreboot/+/54934
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>
diff --git a/src/mainboard/google/zork/variants/baseboard/devicetree_dalboz.cb b/src/mainboard/google/zork/variants/baseboard/devicetree_dalboz.cb
index a8c270e..2525400 100644
--- a/src/mainboard/google/zork/variants/baseboard/devicetree_dalboz.cb
+++ b/src/mainboard/google/zork/variants/baseboard/devicetree_dalboz.cb
@@ -250,6 +250,8 @@
 	register "gpp_clk_config[5]" = "GPP_CLK_OFF"
 	register "gpp_clk_config[6]" = "GPP_CLK_OFF"
 
+	register "pspp_policy" = "DXIO_PSPP_POWERSAVE"
+
 	device cpu_cluster 0 on
 		device lapic 0 on end
 	end