mb/asrock/b85m_pro4: Add missing HWM IRQ on devicetree

Otherwise, there are complaints about it from the allocator.

Change-Id: Ibf6124c3720959154d0b9649871f9bf68a912f14
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/42401
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/asrock/b85m_pro4/devicetree.cb

@@ -103,6 +103,7 @@ chip northbridge/intel/haswell
 					device pnp 2e.b   on		# HWM, LED
 						irq 0x30 = 0xe1		# + Fan RPM sense pins
 						io  0x60 = 0x0290	# + HWM base address
+						irq 0x70 = 0
 					end
 					device pnp 2e.d   off end	# VID
 					device pnp 2e.e   off end	# CIR wake-up