mb/asus/p8z77-m: Disable deep sleep

One can argue whether or not this is desirable, but disabling this means
you cannot use power from the USB ports when the board shuts down, which
is better controlled from an option, but at the very least disabled so
as to replicate default vendor firmware behaviour.

Disable deep sleep like it is disabled on all other variants.

Signed-off-by: Fabian Groffen <grobian@gentoo.org>
Change-Id: I660f2efebf197df055ee7b9c349e4c2b64bda6cf
Reviewed-on: https://review.coreboot.org/c/coreboot/+/75139
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

@@ -81,6 +81,7 @@ chip northbridge/intel/sandybridge
 					device pnp 2e.609 off end	# GPIO 6
 					device pnp 2e.709 off end	# GPIO 7
 					device pnp 2e.14 on end		# Port 80 UART
+					device pnp 2e.16 off end	# Deep sleep
 				end
 				chip drivers/pc80/tpm
 					device pnp 4e.0 on end	# TPM