mb/*/*/devicetree.cb: Normalize disabled PIRQ values

If bit 7 of a PIRQ route is set, it is disabled. Modern OSes don't use
PIRQ routing, so we might as well zero the other bits for consistency.

Tested on Asrock B85M Pro4 with SeaBIOS 1.13.0, still boots.

Change-Id: I78980b9ea5e878a6200df0f6c18c5e7d06a7950a
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/43861
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/mainboard/asus/p5gc-mx/devicetree.cb b/src/mainboard/asus/p5gc-mx/devicetree.cb
index 4c26925..172f65f 100644
--- a/src/mainboard/asus/p5gc-mx/devicetree.cb
+++ b/src/mainboard/asus/p5gc-mx/devicetree.cb
@@ -25,14 +25,14 @@
 		end
 
 		chip southbridge/intel/i82801gx
-			register "pirqa_routing" = "0x8b"
-			register "pirqb_routing" = "0x8a"
-			register "pirqc_routing" = "0x86"
-			register "pirqd_routing" = "0x85"
-			register "pirqe_routing" = "0x83"
+			register "pirqa_routing" = "0x80"
+			register "pirqb_routing" = "0x80"
+			register "pirqc_routing" = "0x80"
+			register "pirqd_routing" = "0x80"
+			register "pirqe_routing" = "0x80"
 			register "pirqf_routing" = "0x80"
 			register "pirqg_routing" = "0x80"
-			register "pirqh_routing" = "0x85"
+			register "pirqh_routing" = "0x80"
 
 			register "gpe0_en" = "0"