util/qemu: Add additional config file for QEMU/Q35

The `q35-alpine.cfg` adds a lot of PCIe devices to resemble the
topology inside an Intel Alpine Ridge Thunderbolt controller.
By no means could this be detected as such a controller. But
having a real-world example of such a topology can help to
test the allocator and other algorithms on a deeper tree.

It adds two levels of PCIe switches (`alpine-root` and
`alpine-1`), and two endpoints (a `pci-testdev` and an xHCI
controller).

It can be added to the default `q35-base.cfg` config, e.g.
with:

    $ make qemu QEMU_EXTRA_CFGS=util/qemu/q35-alpine.cfg

Change-Id: Ieab09c5b67a5aafa986e7d68a6c1a974530408b0
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/51329
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

util/qemu/q35-alpine.cfg

@@ -0,0 +1,61 @@
+# Try to resemble an Alpine Ridge topology
+[device "alpine-root"]
+	driver = "x3130-upstream"
+	bus = "ich9-pcie-port-1"
+	addr = "00.0"
+
+[device "alpine-0"]
+		driver = "xio3130-downstream"
+		bus = "alpine-root"
+		addr = "00.0"
+		chassis = "10"
+
+[device "alpine-nhi"]
+			driver = "pci-testdev"
+			bus = "alpine-0"
+			addr = "00.0"
+			membar = "1M"
+
+[device "alpine-1"]
+		driver = "xio3130-downstream"
+		bus = "alpine-root"
+		addr = "01.0"
+		chassis = "11"
+
+[device "alpine-up"]
+			driver = "x3130-upstream"
+			bus = "alpine-1"
+			addr = "00.0"
+
+[device "alpine-down0"]
+				driver = "xio3130-downstream"
+				bus = "alpine-up"
+				addr = "00.0"
+				chassis = "20"
+
+#					TBT device here
+
+[device "alpine-down1"]
+				driver = "xio3130-downstream"
+				bus = "alpine-up"
+				addr = "01.0"
+				chassis = "21"
+
+#					TBT device here
+
+[device "alpine-down4"]
+				driver = "xio3130-downstream"
+				bus = "alpine-up"
+				addr = "04.0"
+				chassis = "24"
+
+[device "alpine-xhci"]
+					driver = "nec-usb-xhci"
+					bus = "alpine-down4"
+					addr = "00.0"
+
+[device "alpine-2"]
+		driver = "xio3130-downstream"
+		bus = "alpine-root"
+		addr = "02.0"
+		chassis = "12"