mb/asus/p8z77-m: Drop GPIO by I/O

Per Fabian Groffen <grobian@gentoo.org> in CB:75145:

This particular setting results in

[ERROR]  PNP: 002e.308 missing read_resources

The underlying root cause was fixed by commit f5b993de4f
(sio/nuvoton/nct6779d: Correct GPIOBASE virtual LDN). However, to make
GPIO by I/O work requires setting up an I/O port resource here and
a generic LPC I/O decode at southbridge/intel/bd82x6x, and both weren't
done. Even if done, this newfound capability still doesn't offer much.

Change-Id: I39739ab71bc644619667b3e123cc9ad85f9d109f
Signed-off-by: Keith Hui <buurin@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/84617
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: coreboot org <coreboot.org@gmail.com>

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

@@ -77,7 +77,6 @@ chip northbridge/intel/sandybridge
 						drq 0xe6 = 0x7f		# GP7x OD
 					end
 					device pnp 2e.9 off end		# GPIO 8
-					device pnp 2e.308 on end	# GPIO by I/O
 					device pnp 2e.109 on end	# GPIO 1
 					device pnp 2e.209 on		# GPIO 2
 						drq 0xe0 = 0xbf		# GP26 output