mb/asus/p8z77-m: Squelch PNP error about 2e.b irq 70

[ERROR]  PNP: 002e.b 70 irq size: 0x0000000001 not assigned in devicetree

Signed-off-by: Fabian Groffen <grobian@gentoo.org>
Change-Id: I2231afd67031c963045b6e7930d239368c723aa5
Reviewed-on: https://review.coreboot.org/c/coreboot/+/75142
Reviewed-by: Keith Hui <buurin@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/asus/p8x7x-series/variants/p8z77-m/overridetree.cb

@@ -58,6 +58,7 @@ chip northbridge/intel/sandybridge
 						io 0x62 = 0		# SB-TSI address (not used)
 						drq 0xe4 = 0xf9		# GP50, GP52, PWROK#
 						drq 0xf0 = 0x3e		# Enable all fan input debouncers
+						irq 0x70 = 0
 					end
 					device pnp 2e.e off end		# CIR wake-up
 					device pnp 2e.f on		# GPIO PP/OD select