soc/amd/stoney/acpi: Unhide PCI0 root device from OS

In order for Windows to detect/load drivers for any child devices,
the PCI0 root device status must be enabled and visible.

TEST=build google/liara, boot Windows, verify PCI child devices
visible in Device Manager.

Change-Id: I3fb1ba11247f0811120a4cf8a4fd99342ae201de
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/74855
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>

src/soc/amd/stoneyridge/acpi/northbridge.asl

@@ -15,7 +15,7 @@ Method(_BBN, 0, NotSerialized)	/* Bus number = 0 */
 
 Method(_STA, 0, NotSerialized)
 {
-	Return(0x0B)	/* Status is visible */
+	Return(0x0F)	/* Status is visible */
 }
 
 Method(_PRT,0, NotSerialized)