mainboard/google/pyro: Configure PERST pin

Configure GPIO 122 as PERST. This is to assert WiFi PERST
during s0ix entry.

BUG=chrome-os-partner:58112
BRANCH=master
TEST=emerge-pyro coreboot chromeos-bootimage
Change-Id: Id760251a1b037feb62ec43199a145e407b074769
Signed-off-by: Kevin Chiu <Kevin.Chiu@quantatw.com>
Reviewed-on: https://review.coreboot.org/17334
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
diff --git a/src/mainboard/google/reef/variants/pyro/devicetree.cb b/src/mainboard/google/reef/variants/pyro/devicetree.cb
index eb2f133..60729ef 100644
--- a/src/mainboard/google/reef/variants/pyro/devicetree.cb
+++ b/src/mainboard/google/reef/variants/pyro/devicetree.cb
@@ -15,7 +15,7 @@
 	# GPIO for PERST_0
 	# If the Board has PERST_0 signal, assign the GPIO
 	# If the Board does not have PERST_0, assign GPIO_PRT0_UDEF
-	register "prt0_gpio" = "GPIO_PRT0_UDEF"
+	register "prt0_gpio" = "GPIO_122"
 
 	# EMMC TX DATA Delay 1
 	# Refer to EDS-Vol2-22.3.