mb/google/guybrush: set PSPP policy to powersave

BUG=b:188793754

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Change-Id: I262c4c3ae90d8d12fdfe71a3620739070a444a55
Reviewed-on: https://review.coreboot.org/c/coreboot/+/54931
Reviewed-by: Matt Papageorge <matthewpapa07@gmail.com>
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

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

@@ -52,6 +52,8 @@ chip soc/amd/cezanne
 	register "i2c_scl_reset" = "GPIO_I2C0_SCL | GPIO_I2C1_SCL |
 					GPIO_I2C2_SCL | GPIO_I2C3_SCL"
 
+	register "pspp_policy" = "DXIO_PSPP_POWERSAVE"
+
 	register "usb_phy_custom" = "1"
 	register "usb_phy" = "{
 		.Usb2PhyPort[0] = {